How do I get regexp to read specific values in a text file?

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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?
  2 Comments
Brad
Brad on 16 May 2013
Matt, my apologies. I didn't have the aplicable carriage returns in place.

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Accepted Answer

Matt Kindig
Matt Kindig on 16 May 2013
Edited: Matt Kindig on 16 May 2013
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.
  1 Comment
Brad
Brad on 17 May 2013
Matt, thanks for taking a look at this. As I mention below to Cedric, these spaces and tabs are still giving me fits every now and then.

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More Answers (2)

Cedric Wannaz
Cedric Wannaz on 16 May 2013
Edited: Cedric Wannaz on 16 May 2013
I assumed that you forgot the Platform field in the first line of your sample data and took the following instead:
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
You can get all fields as follows:
buffer = fileread('data.txt') ;
pattern = 'form:\s+(\d+).*?Tag:\s+([\d\.]+).*?Bar ID:\s+(\d+)' ;
tokens = regexp(buffer, pattern, 'tokens') ;
data = reshape(str2double([tokens{:}]), 3, []).' ;
and if you are sure that there is only one space after each sem-icolumn, you can use a simpler pattern:
pattern = 'form:\s(\d+).*?Tag:\s([\d\.]+).*?Bar ID:\s(\d+)' ;
Running this leads to a data array with the following columns:
>> data(:,1)
ans =
1
1
23
23
55
>> data(:,2)
ans =
1.0e+04 *
5.5057
5.5123
5.5124
5.5213
5.5300
>> data(:,3)
ans =
9
6
4
9
11
PS: did you see my last comment in the thread with your previous question about regexp? I think that the official doc is really well built and a fantastic resource for learning regexp! :-)
Note that depending the length of the file(s), running three times REGEXP, each time for matching one given field, might be more efficient that running it one time only with the current, more complex pattern.
EDIT: just to clarify, your first attempt was not that bad; you forgot the 'match' 3rd parameter, so REGEXP outputted positions of matches instead of matches (i.e. the first Platform was matched on character 97, the second on character 207, etc). Also your pattern would match e.g. 'Platform: 1' and not just '1'. If you want to match 'Platform: 1' but output just '1', you can either token-ize the expression matching the number in the pattern:
>> pattern_tok = 'Platform:\s(\d+)' ;
>> tokens = regexp(buffer, pattern_tok, 'tokens')
tokens =
{1x1 cell} {1x1 cell} {1x1 cell} {1x1 cell} {1x1 cell}
>> [tokens{:}]
ans =
'1' '1' '23' '23' '55'
which is what Matt proposed, or use a positive look-behind and match the number:
>> pattern_posLb = '(?<=Platform:\s)\d+' ;
>> matches = regexp(buffer, pattern_posLb, 'match')
matches =
'1' '1' '23' '23' '55'
  1 Comment
Brad
Brad on 17 May 2013
Cedric, I've been using the REGEXP function quite a bit lately. Every now and then I still get stuck when trying to account for the spaces and tabs. REGEXP is quite a powerful function. I just used it on another small project handed to me this afternoon. Practice is paying off!! Thanks, again.

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Anver Hisham
Anver Hisham on 18 May 2017
You can use grepValues library,
data = grepValues('data.txt','Platform');

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