combining several marker channels

[Victoria Lishak]

Hi Dr. Bach,

We are analyzing skin conductance responses to positive, negative and neutral sounds. The difficulty is that the conditions are represented by 3 separate marker channels (positive, negative, neutral) in Acqknowlege. We were wondering if there is a way to combine all of them and then specify the conditions for analysis. As it stands, we are only able to run the analysis separately for each marker channel which does not work for us because these stimuli are interspersed.

Thank you very much,

Vicky

[Dominik Bach]

Dear Vicky

this is certainly possible but it requires a tiny bit of matlab coding.

You need to read out the marker channels. Imagine, your marker channels (in the PsPM file) are numbered 5, 6, 7, and your data channels are 1-4. Of course you need to adapt the numbers 5-7 according to the structure of your own data.

Then you can load the data file and read the markers into one variable, for example named 'markers':

load('file name');
markers{1, 1} = data{5}.data(:);
markers{2, 1} = data{6}.data(:);
markers{3, 1} = data{7}.data(:);

All markers are now stored in the variable 'markers'. You can now save them in a new marker channel by first creating a single vector and sorting them:

markers = sort(cell2mat(markers));
data{end+1}=data{5};
data{end}.data=markers;
save('file name', 'infos', 'data');

Or you can use the marker information to specify an onsets file in terms of seconds, for example:

names{1} = 'Event type 1';
onsets{1} = markers{1, 1};

and so on for the second and third event type.

Hope this helps
Best
Dominik

[Victoria Lishak]

Dear Dominik,

Thank you very much for the suggestion. It worked! we were able to combine the channels.

Vicky