MATLAB: How to get regexp to read specific values in a text file

data valuesMATLABregexp

I have a text file containing numerous blocks of data that look like this:

Type: 1 Part ID: 23568 Time Tag: 55012.12345678

Loc ID: 1 Bar ID: 9 Past LR: 0 Isync/Osync: 1

Platform: 1

Type: 1 Part ID: 23568 Time Tag: 55057.12345678

Loc ID: 1 Bar ID: 9 Past LR: 0 Isync/Osync: 1

Platform: 1

Type: 1 Part ID: 23568 Time Tag: 55123.12345678

Loc ID: 1 Bar ID: 6 Past LR: 0 Isync/Osync: 1

Platform: 23

Type: 1 Part ID: 23568 Time Tag: 55124.12345678

Loc ID: 1 Bar ID: 4 Past LR: 0 Isync/Osync: 1

Platform: 23

Type: 1 Part ID: 23568 Time Tag: 55213.12345678

Loc ID: 1 Bar ID: 9 Past LR: 0 Isync/Osync: 1

Platform: 55

Type: 1 Part ID: 23568 Time Tag: 55300.12345678

Loc ID: 1 Bar ID: 11 Past LR: 0 Isync/Osync: 1

Platform: 55

I’m attempting to extract the numeric values for the time tag, Bar ID, and Platform parameters, then store the data separately for plots.

However, I can’t seem to get the proper expression to read the individual values. I’ve tried multiple expressions. The following is the closest I’ve gotten to achieving any values at all:

indata = fileread('data.txt');

pattern = 'Platform:\s\d+';

data = regexp(indata,pattern);

This results in a < 1 x 3 double>

97 207 317

I’ve got to be missing something simple. Any ideas on how to get this to extract the proper values?

Best Answer

This seems to work for me:

pattern = 'Platform:\s+(\d+)';
data = regexp(indata, pattern, 'tokens');
data = cell2mat(cellfun(@(x) str2double(x{:}), data, 'UniformOutput', false));

Others can be done similarly.

EDIT: implemented a better way.

Related Solutions

MATLAB: Can REGEXP map values from different parts of a text file

This seems to work.

    buf = fileread( 'cssm.txt' );
    rex = '(?<=Time Tag: )([\d\.]+).+?(?<=SV ID:[ ]+)(\d+)';
    cac = regexp( buf, rex, 'tokens' );
    cac{:}

returns

    ans = 
        '58548.12345678'    '51'
    ans = 
        '58549.12345678'    '2'
    ans = 
        '58550.12345678'    '2'
    ans = 
        '58551.12345678'    '2'
    ans = 
        '58552.12345678'    '2'
    ans = 
        '58553.12345678'    '1'
    ans = 
        '58554.12345678'    '1'
    ans = 
        '58555.12345678'    '1'
    ans = 
        '58556.12345678'    '3'

where cssm.txt contains your data

.

Comments on the regular expression:

capture tokens
capture the group of digits, which follow after identifiers and space
the "identifiers and space" are used as expressions in look behind operators
thus two groups of (?<= name)( value)
between these two groups: .+?, which is a Lazy Quantifier. It advances the current position one position or more, but only as much of the quantified expression as necessary.
the regular expression must match one sub-string, thus something is needed to match the characters between the two groups to make the two one sub-string. In this case that is done by .+?.

Most of the italic words are copy&paste from the on-line help.

.

BTW: Your pattern works - after a little fixing:

    rex = '*?Tag:\s+([\d\.]+).*?SV ID:\s+([125]{1,2})\W';

but what is the purpose of the leading *? and the trailing \W ?

.

A bit more robust:

    rex = '(?<=Time Tag:)[ ]+([\d\.]+)[^\n]+?(?<=SV ID:)[ ]+(\d+)';

Replacing \s+ between name and value by [ ]+ excludes new-line, tab, etc.
Replacing .*? between the two name-value-pairs by |[^

MATLAB: Can REGEXP be utilized to ignore specific numerical values in a text file

TEXTSCAN is useful for extracting numeric data from strings. Note that the format string I used effectively reads two lines at once by searching for the end of line (\r\n) and ignoring it.

fid = fopen('Brad.txt');
fString = 'Code: %f Firm ID: %f Time Tag: %f %*[\r\n] Board ID: %f SUB ID: %f Error ID: %f Abort: %f';
S = textscan(fid,fString,'CollectOutput',true);
fclose(fid);
Data = S{1};
Data(Data(:,5) == 1 | Data(:,5) == 2 , :) = [];
timeTag = Data(:,3)
abort = Data(:,7)

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