MATLAB: Extract numbers from lines in a txt file. Onset times from experimental data.

behavioralextractfmriget linetxt

Hi,
This problem should be familiar to people working with behavioral data, but I was unable to find a previous answer that would work for me.
I am trying to extract the onset times of certain conditions during an experiment.
The data is organised as in the enclosed file. I want to extract the lines starting with:
'WaitForScanner.OnsetTime'
'Tune.OnsetTime'
and
'ImagineMelody.OnsetTime'
and then extract the numbers at the end of these lines (5-digit onset times in ms) as variables,
work with them a bit in matlab: subtract scanneronset from tuneonset and imagineonset, and convert them to seconds,
and output them in two separate txt files (tuneonset.txt and imagine.txt).
When that works for one subject, I plan to loop over many subjects and also different sessions per subject (different txt file, same principle).
Best,
Andreas

Best Answer

Carrying on from the above that just diddled with the file format to be able to get the data; the following seems to work:
filename = 'Imagine_simple-1-1.txt';
onsets={'Tune.OnsetTime';'ImagineMelody.OnsetTime';'WaitForScanner.OnsetTime'};
imaginefile = 'ImagineMelody.OnsetTime.txt';
tunefile = 'Tune.OnsetTime.txt';
txt=importdata(filename);                % read data file to cellstr array
txt=strrep(txt,char(0),'');              % and convert to char() from 2-byte encoding
txt=strrep(txt,char(255:-1:254),'');     % finally, clean up BOM mess...
fnGrabNum=@(t) (str2double(extractAfter(txt(contains(txt,t)),':'))/1000);  % return numeric data 
times=cellfun(fnGrabNum,onsets,'UniformOutput',0);                         % get the wanted sections
elapsedtimes=seconds(cell2mat(cellfun(@(t) t-times{3},times(1:2),'UniformOutput',0).')); % times from reference time
Results in:
>> elapsedtimes
elapsedtimes = 
  20×2 duration array
    3.233 sec   16.232 sec
   55.402 sec    42.23 sec
   81.644 sec   94.642 sec
   133.88 sec   120.64 sec
   160.07 sec   173.07 sec
   212.27 sec   199.07 sec
   238.45 sec   251.46 sec
   290.68 sec   277.46 sec
   316.91 sec   329.91 sec
   369.07 sec    355.9 sec
   395.25 sec   408.25 sec
   447.46 sec   434.25 sec
   473.69 sec   486.69 sec
   525.86 sec   512.69 sec
   552.03 sec   565.04 sec
   604.22 sec   591.03 sec
    630.4 sec   643.41 sec
    682.6 sec   669.41 sec
   708.79 sec   721.79 sec
   761.16 sec   747.79 sec
>>
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