## ROCPLOT documentation

## CONTENTS

1.0 SUMMARY
2.0 INPUTS & OUTPUTS
3.0 INPUT FILE FORMAT
4.0 OUTPUT FILE FORMAT
5.0 DATA FILES
6.0 USAGE
7.0 KNOWN BUGS & WARNINGS
8.0 NOTES
9.0 DESCRIPTION
10.0 ALGORITHM
11.0 RELATED APPLICATIONS
12.0 DIAGNOSTIC ERROR MESSAGES
13.0 AUTHORS
14.0 REFERENCES

## 1.0 SUMMARY

Provides interpretation and graphical display of the performance of discriminating elements (e.g. profiles for protein families). rocplot reads file(s) of hits from discriminator-database search(es), performs ROC analysis on the hits, and writes graphs illustrating the diagnostic performance of the discriminating elements. Performs ROC analysis on hits files

## 2.0 INPUTS & OUTPUTS

ROCPLOT reads a directory of one or more hits files and writes a text, summary file containing ROC value(s), which are a convenient numerical measure of the sensitivity and specificity of a predictive method. GNUPLOT files for the following graphs are also written.
(i) ROC plots displaying graphically the method sensitivity and specificity.
(ii) Classification plots, which are a useful aid in interpreting ROC plots and ROC values.
(iii) In some modes (see below) a bar chart of the distribution of ROC values is generated.

### 2.1 ROCPLOT modes

ROCPLOT runs in one of two basic modes:
(i) "Single hits file"
(ii) "Multiple hits file".

### 2.1.1 Single hits file mode

ROC analysis is performed on the single hits file. A ROC plot containing one ROC curve and a single ROC value and classification plot are generated.

### 2.1.2 Multiple hits files mode

The same ROC number must be given in the hits files and each file must contain at least this number of non-TRUE hits (see Section 3.1): an error is generated and the program terminates otherwise. In "multiple hits file mode" there are two sub-modes:
(i) "Do not combine data"
(ii) "Combine data".

### 2.1.3 Do not combine data mode

ROC analysis is performed separately for each hits file. Multiple ROC curves are given on the same ROC plot. A ROC value and classification plot are generated for each hits file. A bar chart giving the distribution of ROCn values is also generated. The mean and standard deviation of ROCn values are written to the summary file.

### 2.1.4 Combine data mode

The hits are combined and ROC analysis is performed on the whole (see Section 9.6). A ROC plot containing one ROC curve and a single ROC value and classification plot are generated.
In "combine data" mode there are a further two sub-modes:
(i) "Single gold standard"
(ii) "Multiple gold standard".
These determine how the ROC number and value are calculated.

### 2.1.5 Single gold standard mode

There is a single gold standard (list of known true hits) for the different searches. The same number of known true hits must be specified in the hits files: an error is generated and the program terminates otherwise. The accession number (or other code) and start and end point of each hit must also be given (see Section 3.1).

### 2.1.6 Multiple gold standard mode

There is a gold standard for each different search.
The output in the different modes is summarised (Figure 1).
Figure 1 Summary of ROCPLOT output

                          ____________________________________________________
                          | SINGLE HITS FILE  |      MULTIPLE HITS FILES     |
                          |                   |                |             |
                          |                   | Do not combine |   Combine   |
                          |                   | data           |   data      |
     _____________________|___________________|________________|_____________|
                          |                   |                |             |
     ROC curves / value   | Single            | Multiple (1)   | Single      |
     Bar chart            | -                 | Yes            | -           |
     Classification plot  | Single            | Multiple       | Single      |
     Summary file         | Yes               | Yes            | Yes         |
     _____________________|___________________|________________|_____________|

(1) Multiple ROC curves are given on a single ROC plot.

## 3.0 INPUT FILE FORMAT

### 3.1 Hits files

A hits file contains a list of classified hits that are rank-ordered on the basis of score. The first line must have '>' in the first character position and a space (' ') in the second, then two token - integer pairs delimited by ';'. The integer following 'RELATED' is the total number of known true hits ('relatives') and is the maximum number of TRUE tokens (see below) that could ever appear in the hits file. The integer following 'ROC' is the ROC value that will be calculated. This integer also determines the limit of the x-axes of the ROC and classification plots (see Sections 9.2 & 9.4).
The file then contains a number of lines corresponding to a list of classified hits. The hits *must* be rank-ordered on the basis of score, p-value, E-value etc, with the highest scoring / most significant hit given in the highest rank (1); i.e. on the second line of the file. Other hits should then be given in order of decreasing score / significance.
The first string in a hit line is the classification and must be one of the following: 'TRUE', 'CROSS', 'UNCERTAIN', 'UNKNOWN' or 'FALSE'. If ROCPLOT is run in "Multiple hits files" - "Combine data" - "Single gold standard" modes, each hit line must contain a second string followed by 2 integers. These are required so that ROCPLOT can identify unique hits in the lists of hits (see Section 10.4). For hits to sequences, the string is the accession number (or other database code) and the integers are the start and end point of the hit relative to the full length sequence. For some applications the start and end point data are not required to define unique hits: in these cases the start and end values for all hits should be set to 0 and 1 respectively.

## 4.0 OUTPUT FILE FORMAT

### 4.1 Summary file

The summary file is shown in Figure 3. The first section is comments including the modes ROCPLOT was run in. The file may then contain a section where the file name, number of known true hits and ROCn value are given for each hits file. In cases where data from multiple hits files were combined a single ROCn value will be given instead of this section. The mean and SD of the ROCn values are given if calculated.

### 4.2 GNUPLOT files

ROCPLOT generates various gnuplot driver and data files depending upon mode. For example, the user specifies the base name of the rocplot, classification, bar chart and summary files to be "_rocplot", "_classplot", "_barchart" and "_summary" respectively. If ROCPLOT is run in "Multiple hits files" - "Combine data" - "Single gold standard" mode the following files are generated.

    _classplot_dat0   Data file for classification plot
    _classplot_dat1   Data file for classification plot
    _classplot_dat2   Data file for classification plot
    _classplot_dat3   Data file for classification plot
    _classplot_dat4   Data file for classification plot
    _classplot        Driver file for classification plot
    _rocplot_dat0     Data file for roc plot.
    _rocplot          Driver file for roc plot.
    _summary          Summary file.

If ROCPLOT is run in "Multiple hits files" - "Combine data" - "Single gold standard" mode the following files are generated.

    _classplot0_dat0  Data file for first classification plot
    _classplot0_dat1  ""
    _classplot0_dat2  ""
    _classplot0_dat3  ""
    _classplot0_dat4  ""
    _classplot0       Driver file for first classification plot
    _classplot1_dat0  Data file for second classification plot
    _classplot1_dat1  ""
    _classplot1_dat3  ""
    _classplot1_dat4  ""
    _classplot1       Driver file for second classification plot
    _rocplot_dat0     Data file for roc plot.
    _rocplot_dat1     ""
    _rocplot          Driver file for roc plot.
    _summary          Summary file.

Note that there is no _classplot1_dat2 indicating that the second hits file did not contain any hits for one of the data series (see Section 9.4).
If ROCPLOT is run in "Multiple hits files" - "Do not combine data" the following files are generated.

    _barchart_dat      Data file for bar chart.
    _barchart          Driver file for bar chart.

The plots are visualised by using GNUPLOT, for example by typing load '_classplot1' from the GNUPLOT command line.

### Output files for usage example

### File: _rocplot

    # GNUPLOT driver file for roc plot
    set title "ROC plots for data1.hits & data2.hits (combined - "
    set xlabel "1 - SPEC"
    set ylabel "SENS"
    set nokey
    set noautoscale
    set xrange [0:1]
    set yrange [0:1]
    set key top outside title "Data Series" box 3
    set data style points
    set pointsize 0.45
    plot "_rocplot_dat0" smooth bezier title "Combined dataset (0.185)"

### File: _rocplot_dat0

    # GNUPLOT data file for rocplot, series 0
    0.000    0.007
    0.000    0.014
    0.000    0.021
    0.000    0.029
    0.200    0.029
    0.167    0.036
    0.143    0.043
    0.250    0.043
    0.222    0.050
    0.200    0.057
    0.182    0.064
    0.250    0.064
    0.231    0.071
    0.214    0.079
    0.200    0.086
    0.250    0.086
    0.235    0.093
    0.222    0.100
    0.263    0.100
    0.250    0.107
    0.238    0.114
    0.273    0.114
    0.261    0.121
    0.292    0.121
    0.280    0.129
    0.308    0.129
    0.296    0.136
    0.286    0.143
    0.276    0.150
    0.300    0.150
    0.290    0.157
    0.281    0.164
    0.273    0.171
    0.294    0.171
    0.286    0.179
    0.278    0.186
    0.297    0.186
    0.316    0.186
    0.333    0.186
    0.350    0.186
    0.366    0.186
    0.381    0.186
    0.395    0.186
    0.409    0.186
    0.400    0.193
    0.391    0.200
    0.404    0.200
    0.417    0.200
    0.429    0.200
    0.440    0.200
    0.451    0.200
    0.462    0.200
    0.472    0.200
    0.481    0.200
    0.473    0.207
    0.464    0.214
    0.474    0.214
    0.483    0.214
    0.492    0.214
    0.500    0.214
    0.508    0.214
    0.516    0.214
    0.524    0.214
    0.531    0.214
    0.538    0.214
    0.545    0.214
    0.552    0.214
    0.559    0.214
    0.565    0.214
    0.571    0.214
    0.577    0.214
    0.583    0.214
    0.589    0.214
    0.595    0.214
    0.600    0.214
    0.605    0.214
    0.610    0.214
    0.615    0.214
    0.620    0.214
    0.625    0.214

### File: _classplot

    # GNUPLOT driver file for classification plot
    set title "Classification plot for data1.hits & data2.hits (c"
    set xlabel "Number of hits detected"
    set ylabel "Proportion of hits detected that are of a certain type"
    set nokey
    set key top outside title "Data Series" box 3
    set data style points
    set pointsize 0.45
    plot "_classplot_dat0" smooth bezier title "True hits", "_classplot_dat1" smooth bezier title "Cross hits", "_classplot_dat2" smooth bezier title "Uncertain hits", "_classplot_dat3" smooth bezier title "Unknown hits", "_classplot_dat4" smooth bezier title "False hits"

### File: _classplot_dat0

    # GNUPLOT data file for True hits, series 0
    1.000    1.000
    2.000    1.000
    3.000    1.000
    4.000    1.000
    5.000    0.800
    6.000    0.833
    7.000    0.857
    8.000    0.750
    9.000    0.778
    10.000    0.800
    11.000    0.818
    12.000    0.750
    13.000    0.769
    14.000    0.786
    15.000    0.800
    16.000    0.750
    17.000    0.765
    18.000    0.778
    19.000    0.737
    20.000    0.750
    21.000    0.762
    22.000    0.727
    23.000    0.739
    24.000    0.708
    25.000    0.720
    26.000    0.692
    27.000    0.704
    28.000    0.714
    29.000    0.724
    30.000    0.700
    31.000    0.710
    32.000    0.719
    33.000    0.727
    34.000    0.706
    35.000    0.714
    36.000    0.722
    37.000    0.703
    38.000    0.684
    39.000    0.667
    40.000    0.650
    41.000    0.634
    42.000    0.619
    43.000    0.605
    44.000    0.591
    45.000    0.600
    46.000    0.609
    47.000    0.596
    48.000    0.583
    49.000    0.571
    50.000    0.560
    51.000    0.549
    52.000    0.538
    53.000    0.528
    54.000    0.519
    55.000    0.527
    56.000    0.536
    57.000    0.526
    58.000    0.517
    59.000    0.508
    60.000    0.500
    61.000    0.492
    62.000    0.484
    63.000    0.476
    64.000    0.469
    65.000    0.462
    66.000    0.455
    67.000    0.448
    68.000    0.441
    69.000    0.435
    70.000    0.429
    71.000    0.423
    72.000    0.417
    73.000    0.411
    74.000    0.405
    75.000    0.400
    76.000    0.395
    77.000    0.390
    78.000    0.385
    79.000    0.380
    80.000    0.375

### File: _classplot_dat1

    # GNUPLOT data file for Cross hits, series 1
    1.000    0.000
    2.000    0.000
    3.000    0.000
    4.000    0.000
    5.000    0.200
    6.000    0.167
    7.000    0.143
    8.000    0.250
    9.000    0.222
    10.000    0.200
    11.000    0.182
    12.000    0.250
    13.000    0.231
    14.000    0.214
    15.000    0.200
    16.000    0.250
    17.000    0.235
    18.000    0.222
    19.000    0.263
    20.000    0.250
    21.000    0.238
    22.000    0.273
    23.000    0.261
    24.000    0.250
    25.000    0.240
    26.000    0.231
    27.000    0.222
    28.000    0.214
    29.000    0.207
    30.000    0.233
    31.000    0.226
    32.000    0.219
    33.000    0.212
    34.000    0.235
    35.000    0.229
    36.000    0.222
    37.000    0.216
    38.000    0.211
    39.000    0.205
    40.000    0.200
    41.000    0.195
    42.000    0.190
    43.000    0.186
    44.000    0.182
    45.000    0.178
    46.000    0.174
    47.000    0.170
    48.000    0.167
    49.000    0.163
    50.000    0.160
    51.000    0.157
    52.000    0.154
    53.000    0.151
    54.000    0.148
    55.000    0.145
    56.000    0.143
    57.000    0.140
    58.000    0.138
    59.000    0.136
    60.000    0.133
    61.000    0.131
    62.000    0.129
    63.000    0.127
    64.000    0.125
    65.000    0.123
    66.000    0.121
    67.000    0.119
    68.000    0.118
    69.000    0.116
    70.000    0.114
    71.000    0.113
    72.000    0.111
    73.000    0.110
    74.000    0.108
    75.000    0.107
    76.000    0.105
    77.000    0.104
    78.000    0.103
    79.000    0.101
    80.000    0.100

### File: _classplot_dat2

    # GNUPLOT data file for Uncertain hits, series 2
    1.000    0.000
    2.000    0.000
    3.000    0.000
    4.000    0.000
    5.000    0.000
    6.000    0.000
    7.000    0.000
    8.000    0.000
    9.000    0.000
    10.000    0.000
    11.000    0.000
    12.000    0.000
    13.000    0.000
    14.000    0.000
    15.000    0.000
    16.000    0.000
    17.000    0.000
    18.000    0.000
    19.000    0.000
    20.000    0.000
    21.000    0.000
    22.000    0.000
    23.000    0.000
    24.000    0.000
    25.000    0.000
    26.000    0.038
    27.000    0.037
    28.000    0.036
    29.000    0.034
    30.000    0.033
    31.000    0.032
    32.000    0.031
    33.000    0.030
    34.000    0.029
    35.000    0.029
    36.000    0.028
    37.000    0.054
    38.000    0.053
    39.000    0.051
    40.000    0.050
    41.000    0.049
    42.000    0.048
    43.000    0.047
    44.000    0.045
    45.000    0.044
    46.000    0.043
    47.000    0.064
    48.000    0.062
    49.000    0.061
    50.000    0.060
    51.000    0.059
    52.000    0.058
    53.000    0.057
    54.000    0.056
    55.000    0.055
    56.000    0.054
    57.000    0.070
    58.000    0.069
    59.000    0.068
    60.000    0.067
    61.000    0.066
    62.000    0.065
    63.000    0.063
    64.000    0.062
    65.000    0.062
    66.000    0.061
    67.000    0.060
    68.000    0.059
    69.000    0.058
    70.000    0.057
    71.000    0.056
    72.000    0.056
    73.000    0.055
    74.000    0.054
    75.000    0.053
    76.000    0.053
    77.000    0.052
    78.000    0.051
    79.000    0.051
    80.000    0.050

### File: _classplot_dat3

    # GNUPLOT data file for Unknown hits, series 3
    1.000    0.000
    2.000    0.000
    3.000    0.000
    4.000    0.000
    5.000    0.000
    6.000    0.000
    7.000    0.000
    8.000    0.000
    9.000    0.000
    10.000    0.000
    11.000    0.000
    12.000    0.000
    13.000    0.000
    14.000    0.000
    15.000    0.000
    16.000    0.000
    17.000    0.000
    18.000    0.000
    19.000    0.000
    20.000    0.000
    21.000    0.000
    22.000    0.000
    23.000    0.000
    24.000    0.000
    25.000    0.000
    26.000    0.000
    27.000    0.000
    28.000    0.000
    29.000    0.000
    30.000    0.000
    31.000    0.000
    32.000    0.000
    33.000    0.000
    34.000    0.000
    35.000    0.000
    36.000    0.000
    37.000    0.000
    38.000    0.026
    39.000    0.026
    40.000    0.025
    41.000    0.049
    42.000    0.048
    43.000    0.047
    44.000    0.068
    45.000    0.067
    46.000    0.065
    47.000    0.064
    48.000    0.083
    49.000    0.082
    50.000    0.080
    51.000    0.098
    52.000    0.096
    53.000    0.094
    54.000    0.111
    55.000    0.109
    56.000    0.107
    57.000    0.105
    58.000    0.121
    59.000    0.119
    60.000    0.117
    61.000    0.131
    62.000    0.129
    63.000    0.127
    64.000    0.125
    65.000    0.123
    66.000    0.121
    67.000    0.119
    68.000    0.118
    69.000    0.116
    70.000    0.114
    71.000    0.113
    72.000    0.111
    73.000    0.110
    74.000    0.108
    75.000    0.107
    76.000    0.105
    77.000    0.104
    78.000    0.103
    79.000    0.101
    80.000    0.100

### File: _classplot_dat4

    # GNUPLOT data file for False hits, series 4
    1.000    0.000
    2.000    0.000
    3.000    0.000
    4.000    0.000
    5.000    0.000
    6.000    0.000
    7.000    0.000
    8.000    0.000
    9.000    0.000
    10.000    0.000
    11.000    0.000
    12.000    0.000
    13.000    0.000
    14.000    0.000
    15.000    0.000
    16.000    0.000
    17.000    0.000
    18.000    0.000
    19.000    0.000
    20.000    0.000
    21.000    0.000
    22.000    0.000
    23.000    0.000
    24.000    0.042
    25.000    0.040
    26.000    0.038
    27.000    0.037
    28.000    0.036
    29.000    0.034
    30.000    0.033
    31.000    0.032
    32.000    0.031
    33.000    0.030
    34.000    0.029
    35.000    0.029
    36.000    0.028
    37.000    0.027
    38.000    0.026
    39.000    0.051
    40.000    0.075
    41.000    0.073
    42.000    0.095
    43.000    0.116
    44.000    0.114
    45.000    0.111
    46.000    0.109
    47.000    0.106
    48.000    0.104
    49.000    0.122
    50.000    0.140
    51.000    0.137
    52.000    0.154
    53.000    0.170
    54.000    0.167
    55.000    0.164
    56.000    0.161
    57.000    0.158
    58.000    0.155
    59.000    0.169
    60.000    0.183
    61.000    0.180
    62.000    0.194
    63.000    0.206
    64.000    0.219
    65.000    0.231
    66.000    0.242
    67.000    0.254
    68.000    0.265
    69.000    0.275
    70.000    0.286
    71.000    0.296
    72.000    0.306
    73.000    0.315
    74.000    0.324
    75.000    0.333
    76.000    0.342
    77.000    0.351
    78.000    0.359
    79.000    0.367
    80.000    0.375

### File: _summary

    rocplot summary file (15 Jan 2010)

    mode      == 2 (Multiple input file mode)
    multimode == 2 (Combine data: single ROC plot, single classification plot.)
    datamode  == 1 (Single list of known true relatives.)

    File           Known
    data1.hits     140
    data2.hits     140

    ROC50     == 0.185 (combined)

### File: rocplot.log

    MODE INFO
    modei: 2
    multimodei: 2
    datamodei: 1

    NUMBER OF INPUT FILES
    numfiles: 2

    NAMES ONLY OF INPUT FILES
    hitsnames[0]: data1.hits
    hitsnames[1]: data2.hits

    ROC NUMBER
    roc: 50

    ROC VALUES
    rocn[0]: 0.184714

    COUNT OF HITS
    hitcnt[0]: 80

## 5.0 DATA FILES

ROCPLOT does not use a data file.

## 6.0 USAGE

### 6.1 COMMAND LINE ARGUMENTS

    Performs ROC analysis on hits files
    Version: EMBOSS:6.2.0

       Standard (Mandatory) qualifiers (* if not always prompted):
      [-hitsfilespath]     dirlist    [rocplot] This option specifies the
                                      directory of hits files (input). A 'hits
                                      file'contains a list of hits (e.g. from a
                                      prediction method) that are classified and
                                      rank-ordered on the basis of score, p-value,
                                      E-value etc. The files generated by using
                                      SIGSCAN and LIBSCAN will contain the results
                                      of a search of a discriminating element
                                      (e.g. hidden Markov model, profile or
                                      signature) against a sequence database. The
                                      ROCPLOT application is run on the files to
                                      perform Receiver Operator Characteristic
                                      (ROC) analysis on the hits.
       -mode               menu       [1] This option specifies the mode of
                                      ROCPLOT operation (main mode). In 'single
                                      input file mode', ROC analysis is performed
                                      on the individual hits file; a ROC plot
                                      containing a single ROC curve, and a single
                                      ROC value and classification plot are
                                      generated. In 'multiple input file mode'
                                      there are two sub-modes depending upon
                                      whether (1) ROC analysis is to performed
                                      separately for the individual input files or
                                      (2) the lists of hits in the hits files are
                                      combined and ROC analysis is performed on
                                      the whole (see the ACD option called
                                      'multimode' for more information). If the
                                      input file does not contain at least as many
                                      'FALSE' hits as are specified after the
                                      'ROC' token in the input file, then an error
                                      will be generated and rocplot will
                                      terminate. Where multiple input files are
                                      given as input, each must contain the same
                                      value after the 'ROC' token, or an error
                                      will be generated and rocplot will
                                      terminate. The hits in the hits files *must*
                                      have been rank-ordered on the basis of
                                      score, p-value, E-value etc, with the
                                      highest scoring / most significant hit being
                                      given in the highest rank (1); i.e. on the
                                      second line of the file. Other hits should
                                      then be given in order of decreasing score /
                                      significance. (Values: 1 (Single input file
                                      mode); 2 (Multiple input file mode))
    *  -multimode          menu       [1] This option specifies the mode of
                                      ROCPLOT operation (multimode). In 'Do not
                                      combine data' mode, ROC analysis is
                                      performed separately for the individual
                                      input files. Multiple ROC curves will be
                                      given on the same ROC plot and a ROC value
                                      and a classification plot will be generated
                                      for each input file. A bar chart giving the
                                      distribution of ROCn values, and the mean
                                      and standard deviation of ROCn values are
                                      also generated. In 'Combine data' mode, the
                                      lists of hits in the hits files are combined
                                      and ROC analysis is performed on the whole.
                                      A single ROC curve will be given in the ROC
                                      plot and a single ROC value and
                                      classification plot will be generated. In
                                      this second mode there are two further
                                      sub-modes depending on whether there is (1)
                                      a single list of known true relatives for
                                      the different searches or (2) there is a
                                      different list of known true relatives for
                                      each different search (see the ACD option
                                      called 'datamode' for more information)
                                      (Values: 1 (Do not combine data (multiple
                                      ROC curves in single ROC plot - multiple
                                      classification plots)); 2 (Combine data
                                      (single ROC curve - single classification
                                      plot)))
    *  -datamode           menu       [1] This option specifies the mode of
                                      ROCPLOT operation (datamode). This determine
                                      how the ROC number and value are calculated
                                      in cases where there are multiple input
                                      files (lists of hits) and the user has
                                      specified the data are to be combined. See
                                      rocplot.c for more information. (Values: 1
                                      (Single list of known true relatives); 2
                                      (Multiple lists of known true relatives))
    *  -thresh             integer    [10] This option specifies the overlap
                                      threshold for hits. In cases where the lists
                                      of hits are to be combined and there is a
                                      single set of relatives, the accession
                                      number (or other database identifier code)
                                      of the hit, and the start and end point
                                      respectively of the hit relative to full
                                      length sequence must be provided in the
                                      lists of hits (see 'Input file format'
                                      below). rocplot ensures that only unique
                                      hits are counted when calculating SENS and
                                      SPEC; two hits are 'unique' if they have (i)
                                      different accesssion numbers or (ii) the
                                      same accession numbers but which do not
                                      overlap by any more than a user-defined
                                      number of residues. The overlap is
                                      determined from the start and end points of
                                      the hit. For example two hits both with the
                                      same accession numbers and with the start
                                      and end points of 1-100 and 91 - 190
                                      respectively are considered to be the same
                                      hit if the overlap threshold is 10 or less.
                                      (Any integer value)
      [-outdir]            outdir     [./] This option specifies the directory
                                      where output files are written.
      [-rocbasename]       string     [_rocplot] This option specifies the base
                                      name of ROC plot file(s) (output). A file of
                                      meta data that contains graphs that
                                      illustrate the diagnostic performance of the
                                      discriminator. rocplot generates Receiver
                                      Operating Characteristic (ROC) curves, that
                                      display graphically the sensitivity and
                                      specificity of discriminating elements, and
                                      accompanying ROC value(s), which are a
                                      convenient numerical measure of the
                                      sensitivity and specificity of a method.
                                      Classification plots, which are a valuable
                                      aid in interpreting the ROC plot and value,
                                      are also generated and, depending upon the
                                      mode rocplot is run in, a plot of the
                                      distribution of ROC values. (Any string)
       -outfile            outfile    [_summary] This option specifies the name of
                                      the summary file (output). A text file
                                      summarising the analysis.
    *  -barbasename        string     [_barchart] This option specifies the base
                                      name of bar chart for ROC value distribution
                                      (output). A bar chart giving the
                                      distribution of ROCn values will be
                                      generated when multiple input files (lists
                                      of hits) are provided and the user has
                                      specified 'Do not combine data (multiple ROC
                                      curves). (Any string)
       -classbasename      string     [_classplot] This option specifies the base
                                      name of classification plot file(s)
                                      (output). Classification plots are a
                                      valuable aid in interpreting the ROC plot
                                      and value. A single plot will be generated
                                      where a single input file is provided or
                                      where multiple input files are provided and
                                      the user has specified 'Combine data (single
                                      ROC curve)' mode. Multiple plots will be
                                      generated where multiple input files are
                                      provided and the user has specified 'Do not
                                      combine data (multiple ROC curves)' mode.
                                      (Any string)

       Additional (Optional) qualifiers: (none)
       Advanced (Unprompted) qualifiers:
       -norange            boolean    [N] This option specifies whether to
                                      disregard range data when identifying unique
                                      hits. If set, the range data specified in
                                      the hits files are disregarded, two hits are
                                      classed as unique if they have different
                                      accession numbers (no requirement for
                                      overlapping ranges).
       -logfile            outfile    [rocplot.log] Domainatrix log output file

       Associated qualifiers:

       "-outfile" associated qualifiers
       -odirectory         string     Output directory

       "-logfile" associated qualifiers
       -odirectory         string     Output directory

       General qualifiers:
       -auto               boolean    Turn off prompts
       -stdout             boolean    Write first file to standard output
       -filter             boolean    Read first file from standard input, write
                                      first file to standard output
       -options            boolean    Prompt for standard and additional values
       -debug              boolean    Write debug output to program.dbg
       -verbose            boolean    Report some/full command line options
       -help               boolean    Report command line options and exit. More
                                      information on associated and general
                                      qualifiers can be found with -help -verbose
       -warning            boolean    Report warnings
       -error              boolean    Report errors
       -fatal              boolean    Report fatal errors
       -die                boolean    Report dying program messages
       -version            boolean    Report version number and exit

Qualifier | Type | Description | Allowed values | Default
--- | --- | --- | --- | ---
Standard (Mandatory) qualifiers

[-hitsfilespath]
(Parameter 1)

dirlist

This option specifies the directory of hits files (input). A 'hits file'contains a list of hits (e.g. from a prediction method) that are classified and rank-ordered on the basis of score, p-value, E-value etc. The files generated by using SIGSCAN and LIBSCAN will contain the results of a search of a discriminating element (e.g. hidden Markov model, profile or signature) against a sequence database. The ROCPLOT application is run on the files to perform Receiver Operator Characteristic (ROC) analysis on the hits.

Directory with files

rocplot

-mode

list

This option specifies the mode of ROCPLOT operation (main mode). In 'single input file mode', ROC analysis is performed on the individual hits file; a ROC plot containing a single ROC curve, and a single ROC value and classification plot are generated. In 'multiple input file mode' there are two sub-modes depending upon whether (1) ROC analysis is to performed separately for the individual input files or (2) the lists of hits in the hits files are combined and ROC analysis is performed on the whole (see the ACD option called 'multimode' for more information). If the input file does not contain at least as many 'FALSE' hits as are specified after the 'ROC' token in the input file, then an error will be generated and rocplot will terminate. Where multiple input files are given as input, each must contain the same value after the 'ROC' token, or an error will be generated and rocplot will terminate. The hits in the hits files *must* have been rank-ordered on the basis of score, p-value, E-value etc, with the highest scoring / most significant hit being given in the highest rank (1); i.e. on the second line of the file. Other hits should then be given in order of decreasing score / significance.

1 | (Single input file mode)
2 | (Multiple input file mode)

1

-multimode

list

This option specifies the mode of ROCPLOT operation (multimode). In 'Do not combine data' mode, ROC analysis is performed separately for the individual input files. Multiple ROC curves will be given on the same ROC plot and a ROC value and a classification plot will be generated for each input file. A bar chart giving the distribution of ROCn values, and the mean and standard deviation of ROCn values are also generated. In 'Combine data' mode, the lists of hits in the hits files are combined and ROC analysis is performed on the whole. A single ROC curve will be given in the ROC plot and a single ROC value and classification plot will be generated. In this second mode there are two further sub-modes depending on whether there is (1) a single list of known true relatives for the different searches or (2) there is a different list of known true relatives for each different search (see the ACD option called 'datamode' for more information)

1 | (Do not combine data (multiple ROC curves in single ROC plot - multiple classification plots))
2 | (Combine data (single ROC curve - single classification plot))

1

-datamode

list

This option specifies the mode of ROCPLOT operation (datamode). This determine how the ROC number and value are calculated in cases where there are multiple input files (lists of hits) and the user has specified the data are to be combined. See rocplot.c for more information.

1 | (Single list of known true relatives)
2 | (Multiple lists of known true relatives)

1

-thresh

integer

This option specifies the overlap threshold for hits. In cases where the lists of hits are to be combined and there is a single set of relatives, the accession number (or other database identifier code) of the hit, and the start and end point respectively of the hit relative to full length sequence must be provided in the lists of hits (see 'Input file format' below). rocplot ensures that only unique hits are counted when calculating SENS and SPEC; two hits are 'unique' if they have (i) different accesssion numbers or (ii) the same accession numbers but which do not overlap by any more than a user-defined number of residues. The overlap is determined from the start and end points of the hit. For example two hits both with the same accession numbers and with the start and end points of 1-100 and 91 - 190 respectively are considered to be the same hit if the overlap threshold is 10 or less.

Any integer value

10

[-outdir] (Parameter 2) | outdir | This option specifies the directory where output files are written. | Output directory | ./

[-rocbasename]
(Parameter 3)

string

This option specifies the base name of ROC plot file(s) (output). A file of meta data that contains graphs that illustrate the diagnostic performance of the discriminator. rocplot generates Receiver Operating Characteristic (ROC) curves, that display graphically the sensitivity and specificity of discriminating elements, and accompanying ROC value(s), which are a convenient numerical measure of the sensitivity and specificity of a method. Classification plots, which are a valuable aid in interpreting the ROC plot and value, are also generated and, depending upon the mode rocplot is run in, a plot of the distribution of ROC values.

Any string

_rocplot

-outfile | outfile | This option specifies the name of the summary file (output). A text file summarising the analysis. | Output file | _summary
-barbasename | string | This option specifies the base name of bar chart for ROC value distribution (output). A bar chart giving the distribution of ROCn values will be generated when multiple input files (lists of hits) are provided and the user has specified 'Do not combine data (multiple ROC curves). | Any string | _barchart

-classbasename

string

This option specifies the base name of classification plot file(s) (output). Classification plots are a valuable aid in interpreting the ROC plot and value. A single plot will be generated where a single input file is provided or where multiple input files are provided and the user has specified 'Combine data (single ROC curve)' mode. Multiple plots will be generated where multiple input files are provided and the user has specified 'Do not combine data (multiple ROC curves)' mode.

Any string

_classplot

Additional (Optional) qualifiers
(none)
Advanced (Unprompted) qualifiers
-norange | boolean | This option specifies whether to disregard range data when identifying unique hits. If set, the range data specified in the hits files are disregarded, two hits are classed as unique if they have different accession numbers (no requirement for overlapping ranges). | Boolean value Yes/No | No
-logfile | outfile | Domainatrix log output file | Output file | rocplot.log
Associated qualifiers
"-outfile" associated outfile qualifiers
-odirectory | string | Output directory | Any string |
"-logfile" associated outfile qualifiers
-odirectory | string | Output directory | Any string |
General qualifiers
-auto | boolean | Turn off prompts | Boolean value Yes/No | N
-stdout | boolean | Write first file to standard output | Boolean value Yes/No | N
-filter | boolean | Read first file from standard input, write first file to standard output | Boolean value Yes/No | N
-options | boolean | Prompt for standard and additional values | Boolean value Yes/No | N
-debug | boolean | Write debug output to program.dbg | Boolean value Yes/No | N
-verbose | boolean | Report some/full command line options | Boolean value Yes/No | Y
-help | boolean | Report command line options and exit. More information on associated and general qualifiers can be found with -help -verbose | Boolean value Yes/No | N
-warning | boolean | Report warnings | Boolean value Yes/No | Y
-error | boolean | Report errors | Boolean value Yes/No | Y
-fatal | boolean | Report fatal errors | Boolean value Yes/No | Y
-die | boolean | Report dying program messages | Boolean value Yes/No | Y
-version | boolean | Report version number and exit | Boolean value Yes/No | N

### 6.2 EXAMPLE SESSION

An example of interactive use of ROCPLOT is shown below. Here is a sample session with rocplot

    % rocplot
    Performs ROC analysis on hits files
    Hits directories [rocplot]: rocplot/hitsin
    Available modes
             1 : Single input file mode
             2 : Multiple input file mode
    Select mode of operation. [1]: 2
    Available modes
             1 : Do not combine data (multiple ROC curves in single ROC plot - multiple classification plots)
             2 : Combine data (single ROC curve - single classification plot)
    Select mode of operation. [1]: 2
    Available modes
             1 : Single list of known true relatives
             2 : Multiple lists of known true relatives
    Select mode of operation. [1]: 1
    Overlap threshold for hits. [10]:
    General output file output directory [./]:
    Base name of ROC plot file(s) (output). [_rocplot]:
    Rocplot summary output file [_summary]:
    Base name of classification plot file(s) (output). [_classplot]:

    /homes/user/test/data/structure/rocplot/hitsin/data1.hits
    /homes/user/test/data/structure/rocplot/hitsin/data2.hits
    Processing data1.hits
    Processing data2.hits
    Please wait ... done!

Go to the output files for this example

## 7.0 KNOWN BUGS & WARNINGS

GNUPLOT must be started in the same directory as the gnuplot data files.
If you run ROCPLOT on many input files without specifying combination of data the ROC plot generated can get very cluttered. This is not a flaw of ROCPLOT, but an inevitable consequence of trying to draw too many things on the same plot. The recomended maximum is 5 to 10 input files.
The hits in the hits files *must* be rank-ordered on the basis of score, p-value, E-value etc, with the highest scoring / most significant hit given in the highest rank (1); i.e. on the second line of the file. Other hits should then be given in order of decreasing score / significance.

## 8.0 NOTES

Future implementation
1. Accept a feature file as input.
2. Split ROCPLOT into separate programs, one for each of the major modes.
Description of 'sort' mode (additional option in ACD)
This option specifies whether to process the input files in blocks (of the same domain identifier). In this case the analysis mode (mode-multimode-datamode) are set to Multiple input file - combine data - Single list of known true relatives (2-2-1) and the analysis is performed on each block of hits files with the same domain identifier. In the output file, ROC values are given for each combined analysis and the mean and SD of all the combined analyses are given. The domain identifier is defined as the text between the first and second period ('/.') in the input file name.
Description of 'norange' mode (additional option in ACD)
This option specifies whether to disregard range data when identifying unique hits. If set, the range data specified in the hits files are disregarded, two hits are classed as unique if they have different accession numbers (no requirement for overlapping ranges).

### 8.1 GLOSSARY OF FILE TYPES

FILE TYPE | FORMAT | DESCRIPTION | CREATED BY | SEE ALSO

Hits file

Text file of classified hits

A list of hits (e.g. from a prediction method) that are classified and rank-ordered on the basis of score, p-value, E-value etc.

ROCON and LIBSCAN (hits from searches of a discriminating element (hidden Markov model, profile or signature) against a sequence database).

ROCPLOT is run on the files to perform Receiver Operator Characteristic (ROC) analysis on the hits.

None

## 9.0 DESCRIPTION

Predictive methods are a mainstay of bioinformatics. Discrciminating elements such as hidden Markov models (HMM), sparse protein signatures and profiles can be generated for a set of proteins with related sequence, structural or functional properties. These discriminators are characteristic of the property considered and can be used diagnostically, for instance, by screening a database of uncharacterised sequences. When assessing predictive performance a "gold standard" of truth is required. This is a set of examples that are known to be related to the discriminating element, and, ideally, a further set that is known to be definitely not related. For example, to assess a protein family HMM to detect true members of that family requires, at least, a list of the known family members. If a method works well for the "gold standard" we can infer it will work well generally. Traditionally, swissprot annotation was used but this is somewhat unreliable because the annotation is derived from sequence comparison as well as experimental data. Increasingly, use is made of databases such as SCOP, in which sequence, structural and functional relationships are classified. As an aside, such databases are biased for domains, which are the unit of classification, so it's important to check that a method tested on e.g. SCOP will also work on full-length sequences.

### 9.1 Sensitivity and specificity

Most predictive methods can be placed into two broad groupings: (i) Methods that produce a definite yes/no answer. There is a single list of "hits" and things not in this list are "misses". (ii) Methods that produce a list of hits that is rank-ordered on the basis of the score or p-value of the discrimintor-sequence match. The hit with the highest / most significant score will be in highest rank, i.e. rank 1. Usually, a cutoff value of rank, score or p-value is applied; "hits" occur at and above the cuttoff and "misses" occur below it.
Armed with the notion of a "gold standard" and "hits" and "misses", all hits retrieved by a search can be organised as in Figure 4.
Figure 4 Classification of hits

                     From the gold standard
                    |          |          |
                    | Related  | Unrelated|
             _______|__________|__________|_______
                    |          |          |
    S r      (+ve)  |    TP    |    FP    |   P   (=TP+FP)
    e e      hits   |          |          |
    a s      _______|_ ________|__________|_______
    r u             |          |          |
    c l      (-ve)  |    FN    |    TN    |   N   (=FN+TN)
    h t      misses |          |          |
             _______|__________|__________|_______
                    |          |          |
                    |    R     |    U     |
                    | (=TP+FN) | (=FP+TN) |

Where TP are true positives, FN are false negatives, R (TP+FN) is the total number of known true hits (relatives). FP are false positives, TN are true negatives and U (FP+TN) is the total number of known non-relatives. The number of positives is given by P (TP+FP) and the number of misses by N (FN+TN).
The two basic types of error are where (i) a relationship is missed ("false negative" or "ommission error") and (ii) a relationship is inferred which does not truly exist ("false positive" or "commission error"). The cost of these two errors are not usually equal: it depends on the specific application but usually false positives are worse than false negatives. A crude way to measure the performance is to quote ommission and commission error rates at a fixed cutoff value to the list of hits. These rates are usually given as sensitivity (SENS or "coverage") and specificity (SPEC or "accuracy") of the method and are defined as follows.
SENS = TP / R
SPEC = TP / P
Another measure of specificity (JMB 282, 903-918) defines SENS = TN / U. The measure used depends on the specific application, but TP/P is often most suitable as it reflects the hits that are actually retrieved by the search. TP / P is used in ROCPLOT (see Section 10.2).
The most basic graphical representation of sensitivity and specificity is the "coverage versus error plot" or "sensitivity curve" (Figure 5). This plots the number of true positives detected (y-axis) versus the number of false positives detected (x-axis), at different cutoff values in the list of hits. The word 'detected' here refers to a hit that is above the cutoff, i.e. is of a higher or more significant score.
Figure 5 A "coverage versus error" plot

                |
                |                           *
     No. true   |                    *
     positives  |              *
     detected   |          *
                |       *
                |     *
                |   *
                |  *
                | *
                |*
                |______________________________
                                     No. false
                                     positives
                                     detected

### 9.2 ROC plot

A superior measure of diagnostic performance is to use Receiver Operator Characteristic (ROC) curves to display graphically the sensitivity and specificity of a method. ROC analysis is a powerful aid to interpretation and has been widely used, for instance to evaluate clinical diagnostic tests and in the bioinformatics literature. A ROC curve (Figure 6) is a generalised version of the "coverage versus error" plot. It plots SENS (TP/R) on the y-axis, i.e. the fraction of known true hits detected or the "rate of true positives", versus 1-SPEC (1 - TP/P) on the x-axis, i.e. 1 minus the fraction of detected hits that are true positives or the "rate of false positives". ROC curves are generated by plotting SENS versus (1-SPEC) for all possible cutoff values in a rank-ordered list of hits.
Figure 6 A ROC curve

                |
                |                           *
        SENS    |                    *
                |              *
      "rate of  |          *
        true    |       *
     positives" |     *
                |   *
                |  *
                | *
                |*
                |______________________________
     	                     1 - SPEC
                         "rate of false positives"

The first image is a schematic, the second is a screenshot of the a ROCPLOT-generated roc plot, visualised by using GNUPLOT.
A ROC curve shows the trade-off between sensitivitiy and specificity: as sensitivitiy increases, specificity decreases. The ideal ROC curve lies on the y-axis, i.e. there is perfect discrimination between related and unrelated proteins. A ROC curve for a good prediction should always be to the left of the diagonal. ROC curves are very useful for comparing two diffent methods (e.g. homology search methods) because if one method produces a curve to the left of another then that method is superior, regardless of the cost of ommission and commission errors.

### 9.3 ROC value

The area under the ROC curve (AUROC) gives the probability of a correct classification and is a very convenient numerical measure of the sensitivity and specificity of a method. Areas are relative to a ROC space which is a unit square in which both SENS and SPEC are plotted from 0 to 1. An area of 0.9 for example means that a sequence from the group of known relatives has a probability of 0.9 of scoring higher than a sequence from the group of known non-relatives. The best possible prediction has an AUROC of 1.
In most cases however there are vastly more true negatives than true positives. This is the case when a search is made with a sequence against a large sequence database. As most sequence are quite discriminating for their family, the AUROC for a ROC curve plotted for the results of the entire database search will be very close to 1. The AUROC value is still useful but it has to be calculated to 5 or 6 decimal places. Furthermore all the curves would look identical which makes comparing two methods by eye impossible, all the database scores would have to be written to disk, and the value does not really represent the way in which the average biologist, who is unprepared to inspect many thousands of false positives, would use the method. For these reasons, ROC curves are usually truncated to the first 50 or 100 false hits, and the so-called ROC50 or ROC100 value calculated. ROCn values are quicker and more convenient to calculate, can be expressed by fewer decimal places and reflect the way in which the average biologist will use the method.

### 9.4 Classification plot

In many cases not every hit returned by a search can be clearly classified as true or false or it might otherwise be desirable to manage hits with an intermediate classification. This might be the case where the gold standard is based on a hierarchic structure (e.g. SCOP). Consider conceptual "cross", "uncertain" and "unknown" hits. "Cross hits" have a definite relation to the query but not at such a fine level as a "true" hit. An example is a query matching a sequence belonging to a different family but the same superfamily as the query. An "uncertain hit" might show some but not clear evidence of a relation. An example would be a query matching a sequence belonging to a different family and superfamily, but the same fold as the query. For other hits, nothing may be known either way and these would be classified as "unknown". ROCPLOT supports "cross", "uncertain" and "unknown" hits and provides a graphical representation of the classifications of hits by generating a "classification plot".
A classification plot (Figure 7) shows the proportion of hits detected that are 'true', 'cross', 'uncertain', 'unknown' and 'false'. The y-axis is the proportion of the hits detected that are of a certain type, the x-axis is the proportion of the total number of hits detected. A separate curve is given for hits of each type. In ROCPLOT a classification plot is generated by plotting these proportions at each rank in the list of hits up to the point where a user-defined number of 'false' hits are detected. As ROC plots and values (see below) do not consider 'cross', 'uncertain' and 'unknown' hits, the classification plot is a useful aid in interpreting the ROC plot and value for some applications.
Figure 7 A classification plot

     Proportion of 1.0|
     hits detected    |
     that are of a    |
     certain type     |
                      |                       *     *  TRUE
                      |              *        .     .  CROSS
                      |        *      .
                      |    *   .
                      |  *  .                    x  x  FALSE
                      | *.              x
                      |*.          x
                      |______________________________
                     0                              1.0
                                     Proportion of total
                                     number of hits detected.

The first image is a schematic (hits of classification 'uncertain' and 'unknown' are not shown for clarity). The second is an screenshot of the a ROCPLOT-generated classification plot, visualised by using GNUPLOT.

### 9.5 Processing multiple lists of hits (no combination of lists)

ROC analysis is a powerful way to compare predictive methods side by side. A ROC value can be generated for each method and a curve plotted on the same ROC plot. For some applications a summary of a set of ROC values is required. Depending upon mode (see Section 2.1), ROCPLOT will generate the mean, standard deviation (SD) and a bar chart (Figure 8) of the distribution of ROCn values. In constructing the bar chart, the range of possible ROC values from 0 to 1 is divided into 20 bins of size 0.05 and the frequency of occurence of ROC values in each bin range is calculated.
Figure 8 Bar chart for distribution of ROCn values

    Frequency   |
                |                        ___
                |                       |   |
                |                    ___|   |
                |            ___    |   |   |
                |           |   |   |   |   |
                |    ___    |   |   |   |   |
                |   |   |___|   |   |   |   |
                |   |   |   |   |___|   |   |
                |___|   |   |   |   |   |   |
                |   |   |   |   |   |   |   |
                |___|___|___|___|___|___|___|__

                             Bins for different
                             ranges of value of
                             ROCn value

### 9.6 Processing multiple lists of hits (combination of lists)

In some cases it is desirable to combine data from multiple lists of hits and derive a single ROC curve and value. Such cases fall into one of two broad groups: (i) There is a single set of known true relatives for the different searches, for example, when assessing the performance of multiple discriminating elements for a single family. In these cases the typical ROC50 or ROC100 value is generated. (ii) There is a different set of known true relatives for each different search, for example, when assessing the performance of a single discriminating element over mutliple families. A much higher ROC number is used. For exmaple, ROC500 is reasonable if 10 lists of hits are combined.
Lists of hits arising from different searches can be combined and reordered if they are scored on the same scoring scale or have been assigned a p-value. In principle one way to use ROCPLOT is to do the combination and reordering yourself and provide ROCPLOT with a single list of hits as input. This, however, is not possible if the lists of hits use different scoring schemes and a p-value is not available. Furthermore, in many cases the relative positioning of hits in the list is more important than the absolute score. If two lists of hits (A and B) whose hits lie on different regions of the same scoring scale are merged and reordered, true hits, which rank very highly in their own list (A), might be relegated way down the merged list, appearing after false hits from list B. Therefore the high-ranking and potentially interesting hits in list A might, depending on the ROCn value calculated, not be considered in the combination ROC value. To overcome this, the lists of hits can be processed in parallel: to consider all the hits at rank 1 in the different lists first, then all the hits at rank 1 and 2, and so on. This is the approach taken in ROCPLOT (see Section 10).

## 10.0 ALGORITHM

### 10.1 Classification plot

The proportion of the total hits detected that are of a certain type (TRUE, CROSS, UNCERTAIN, UNKNOWN and FALSE) is calculated at each rank position in the list of hits, from the first rank (hit) up to and including the hit corresponding to the nth false positive. n is the ROC number given in the hits file. For example, if i is the current rank number, Proportion(TRUE) = (Number of TRUE tokens from ranks 1 to i / i).

### 10.2 ROC plot

### 10.2.1 "Single hits file" mode and "Multiple hits files - Do not combine data" mode

SENS and SPEC are calculated at each rank in the list of hits from the first rank up to and including the hit that is the nth false positive. n is the ROC number given in the hits file. SENS and SPEC are calculated as follows.
SENS(i) = TP / R
SPEC(i) = TP / i
Where i is the current rank number, TP is the number of TRUE tokens occuring from rank 1 to i. R is the total number of known true hits (relatives) specified after the 'RELATED' token in the hits file(s) (see Section 3.1).
Hits classified as CROSS, UNCERTAIN and UNKNOWN are all treated as FALSE. This means that the ROC curve is really giving "rate of noise" on the x-axis rather than the "rate of false positives". The "noise" might actually include genuinely interesting hits and for this reason, the ROC plot must be interpreted in the light of the classification plot if CROSS, UNCERTAIN and UNKNOWN classifications are used. If the hits file contains fewer than n hits that are non-TRUE, an error is generated and ROCPLOT terminates.

### 10.2.2 "Multiple hits files" / "Combine data" mode

SENS and SPEC are calculated at different ranks as before but this time the lists are processed in parallel. SENS and SPEC are calculated from each list in turn at each rank from the first rank up to and including the rank at which n false positive (from the different lists) are detected. If there are 5 hits files for example, a maximum of 5 hits are considered to yield up to 5 SENS and 5 SPEC values at each rank. In "Single gold standard" mode, n is the ROC number specified after the 'ROC' token in the hits files. In "Multiple gold standard" mode, n = (ROC number from hits files * number of input files). SENS and SPEC are calculated as follows.
SENS(i, j) = TP / R
SPEC(i, j) = TP / nhits
Where i is the current rank number and j is the number of the list of the hit being considered. TP is the number of true positives. TP = (Number of TRUE tokens in ranks 1 to i-1 in all lists + number of TRUE tokens in rank i in lists 1 to j). Note that in "Single gold standard" mode only those TRUE tokens corresponding to unique hits (see below) are counted. R is the number of known 'true' hits (relatives). In "Single gold standard" mode, R equals the value after the 'RELATED' token in the hits files. In "Multiple gold standard" mode, R equals the sum of the values given after the 'RELATED' tokens. nhits is the number of hits considered so far. If the hits files contain equal numbers of hits, nhits = (i-1)*N + j, where N is the total number of hits files.

### 10.3 ROC value

### 10.3.1 "Single hits file" mode and "Multiple hits files - Do not combine data" mode

The ROCn value is defined as:
ROCn = 1/nR * T (T is Ti summed for 1<=i<=n)
n is the ROC number from the hits file. R is the total number of known true hits given in the hits file after the 'RELATED' token. Ti is the number of TRUE tokens occuring from rank 1 up to the rank for the ith non-TRUE hit. In other words, Ti is the number of 'true' hits detected above the ith 'false' hit.

### 10.3.2 "Multiple hits files" / "Combine data" mode

Again, the ROCn value is defined as :
ROCn = 1/nR * T (T is Ti summed for 1<=i<=n)
n is the ROC number used. In "Single gold standard" mode, n is the ROC number given in the hits files. In "Multiple gold standard" mode, n = (ROC number given in hits files * number of input files). R is the number of known true hits (relatives). In "Single gold standard" mode, R equals the value given after the 'RELATED' token in the hits files. In "Multiple gold standard" mode, R equals the sum of the values given after the 'RELATED' tokens.
Ti is the number of TRUE tokens found up to the ith token that is not 'TRUE'. If k and j are the rank and number of list respectively at which the nth non-TRUE hit is detected, Ti = (number of TRUE tokens in ranks 1 to k-1 in all lists + number of TRUEn tokens in rank k in lists 1 to j). Again, Ti is the number of 'true' hits detected above the ith 'false' hit.

### 10.4 Identifying unique hits

In "Multiple hits files" - "Combine data" - "Single gold standard" mode, ROCPLOT only counts unique hits when calculating SENS and SPEC. Two hits are 'unique' if they have (i) different accesssion numbers or (ii) the same accession numbers but which do not overlap by any more than a user-defined number of residues. The overlap is determined from the start and end points of the hit. For example two hits, with the same accession numbers and start and end points of 1-100 and 91 - 190 respectively, are not unique if the overlap threshold is 10 or less. Duplicate hits (the second and subsequent occurences of non-unique ones) in the hits files are discarded - they are NOT considered when calculating the ROC curve and value.
The different hits files might contain different numbers of hits and therefore at higher ranks, SENS and SPEC might only consider hits from a subset of all the hits files, up to the last rank for which it is likely just a single hit will be considered. This is illustrated in Figure 9, which shows the lists of hits for 3 hits files, a ROC number of 3 is given for each one. At ranks 1 up to 6, SENS and SPEC would consider hits from all 3 input files. At rank 7 however, only hits from files 2 and 3 would be considered as 3 false hits have been detected in file 1 and no more hits are listed. Similarly at ranks 10 and 11 only hits from file 3 will be considered.
Figure 9 Calculation of ROC value for multiple hits files

    Rank  File1  File2  File3
          ROC3   ROC3   ROC3
    1     TRUE   TRUE   TRUE
    2     TRUE   TRUE   TRUE
    3     TRUE   TRUE   TRUE
    4     FALSE  TRUE   TRUE
    5     FALSE  TRUE   TRUE
    6     FALSE  FALSE  TRUE
    7            FALSE  FALSE
    8            TRUE   FALSE
    9            FALSE  TRUE
    10                  TRUE
    11                  FALSE

## 11.0 RELATED APPLICATIONS

## See also

Program name | Description
--- | ---
contacts | Generate intra-chain CON files from CCF files
domainalign | Generate alignments (DAF file) for nodes in a DCF file
domainrep | Reorder DCF file to identify representative structures
domainreso | Remove low resolution domains from a DCF file
interface | Generate inter-chain CON files from CCF files
libgen | Generate discriminating elements from alignments
matgen3d | Generate a 3D-1D scoring matrix from CCF files
psiphi | Calculates phi and psi torsion angles from protein coordinates
rocon | Generates a hits file from comparing two DHF files
seqalign | Extend alignments (DAF file) with sequences (DHF file)
seqfraggle | Removes fragment sequences from DHF files
seqsearch | Generate PSI-BLAST hits (DHF file) from a DAF file
seqsort | Remove ambiguous classified sequences from DHF files
seqwords | Generates DHF files from keyword search of UniProt
siggen | Generates a sparse protein signature from an alignment
siggenlig | Generates ligand-binding signatures from a CON file
sigscan | Generates hits (DHF file) from a signature search
sigscanlig | Searches ligand-signature library & writes hits (LHF file)

## 12.0 DIAGNOSTIC ERROR MESSAGES

For purposes of generating the ROC plot and ROC curve, hits classified as CROSS, UNCERTAIN and UNKNOWN are all treated as FALSE. An error is generated and ROCPLOT terminates in the following cases.
If the hits file contains more TRUE hits than the number after the 'RELATED' token.
In "Multiple hits files" mode, if different values are given after the 'ROC' token in the files.
The number of non-TRUE hits is less than the value after the 'ROC' token.
In "Single gold standard" mode, if different values are given after the 'RELATED' token in the files.

## 13.0 AUTHORS

Jon Ison (jison@ebi.ac.uk)
The European Bioinformatics Institute Wellcome Trust Genome Campus Cambridge CB10 1SD UK

## 14.0 REFERENCES

Please cite the authors and EMBOSS.
Rice P, Longden I and Bleasby A (2000) "EMBOSS - The European Molecular Biology Open Software Suite" Trends in Genetics, 15:276-278.

See also http://emboss.sourceforge.net/

### 14.1 Other useful references

Gribskov M, Robinson NL. 1996. Use of Receiver Operating Characteristic (ROC) Analysis to Evaluate Sequence Matching. Computers & Chemistry 20(1): 25-33.