extract data un 2D array to create 3d array

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alice dormeuil
alice dormeuil 2018-4-16
回答： alice dormeuil 2018-4-20
Hello,
I'm new on Matlab, and I would like to create a 3D array by extracting data in a 2D array.
I Have an array, containing eye data during multiple Trials, which size is 6942173x1cell (the attached file is smaller in order to attached it). Each trial start with 'MSG Number... Recenter Cue Event'. I would like to extract data of each trial and to create a 3D array containing each trial data in different pages.
I created this code but the loop doesn't work, it extracts only the first trial and doesn't create a 3D array.
idx1 = find(~cellfun('isempty',strfind(Edf,'Recenter Cue Event')));
for i=1:1:size(Edf)
for k=1:size(idx1)
if i==idx1(k)
Edf_Trials(:,:,k)=Edf(idx1(k):idx1(k+1)-1);
else
i=i+1;
end
end
end
Thank you for your help
Alice
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alice dormeuil
alice dormeuil 2018-4-18
i = 12968 and k = 1 so the code is running correctly for the first part. As I removed the else portion I have an error message 'Subscripted assignment dimension mismatch'.
Bob Thompson
Bob Thompson 2018-4-18
I'm assuming the error message occurs on this line:
Edf_Trials(:,:,k)=Edf(idx1(k):idx1(k+1)-1);
If so, then it is most likely because you can't have k+1 when k=size(idx1). I would suggest writing an if statement that looks for this condition and just tells the Edf range to go to the end. This can be part of your current if statement, but the condition needs to come before what you have now.
if k == size(idx1,1)
...
elseif i == idx1(k)
...
end
Also, I would suggest it is good coding practice to specify a single dimension when using size() or to use two variables as outputs.
[row, col] = size(idx1);
By making those two changes your code seemed to run fine for me with a bunch of dummy data. This makes me think that the bug is in the recognition of 'Recenter Cue Event'. What is the value of idx1 when you run it? (I know you included a sample of your data, and thank you, but for personal paranoia reasons I don't download things off this site.)

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alice dormeuil
alice dormeuil 2018-4-20

Hi, Thanks for your suggestion which help me to find the solution. The problem was :

  • the size of the trials was different among the trial, so I have to create a cell array with {}
  • effectively the other problem was k+1 doesn't exist when k=size(idx1).

the new code I made is :

idx1 = find(~cellfun('isempty',strfind(Edf,'Recenter Cue Event')));
for i=1:1:size(Edf)
    for k=1:(size(idx1)-1)
        if i==idx1(k)
            Edf_Trials(:,1,k)={Edf(idx1(k):idx1(k+1)-1)};
        end
    end
end
k=size(idx1);
Edf_Trials(:,1,k)={Edf(idx1(k):end)};

And It's perfectly working.

Thanks again for your help.

Alice

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