How to alternatively cut a signal into segments of different sizes

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Rida Alfonso 2020-6-3

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https://ww2.mathworks.cn/matlabcentral/answers/541730-how-to-alternatively-cut-a-signal-into-segments-of-different-sizes

评论： Mohammad Sami 2020-6-8

I have an EMG signal of duration 680 seconds, i want to make segments of this signal starting from the 1st 6 seconds and then the next 8 seconds and repeat this procedure till i have reached 680 seconds;i want to make alternative segments of 6s and 8s and then i want to concatenate the 6s data into 1 variable and 8 seconds into another variable. The final step is to to grow size of the 6s variable to 8s so that both the variables becomes of the same time. 6 seconds represents rest while the next 8s represents contraction. This set is repeated 10 times like rest for 6s and then contraction for the next 8s.

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Mohammad Sami 2020-6-4

What is the sampling frequency of the data tahat you uploaded ?

Rida Alfonso 2020-6-4

编辑：Rida Alfonso 2020-6-4

2048Hz

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Mohammad Sami 2020-6-4

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https://ww2.mathworks.cn/matlabcentral/answers/541730-how-to-alternatively-cut-a-signal-into-segments-of-different-sizes#answer_445967

编辑：Mohammad Sami 2020-6-4

在 MATLAB Online 中打开

You can use reshape to extract the signals

% Incorrect : prb2 = reshape(prb,14*2048,2,[]);
% Correction
prb2 = reshape(prb,14*2048,[],2);
prbsix = prb2(1:(6*2048),:,:);
prbeight = prb2((6*2048+1):end,:,:);
prbsix = [ prbsix ; zeros(2*2048,size(prbsix,2),size(prbsix,3))]; % pad with zeros

If you wish to reshape it back to 2D, you can do as follows

prbeight = reshape(prbeight,[],2);
prbsix = reshape(prbsix,[],2);

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Rida Alfonso 2020-6-4

If i were to do the same procedure for three channels (nx3 matrix) , would it be right to use the code as follows

% reshape signal into 14 seconds block

prb2 = reshape(prb,14*2048,[],3);

% extract six second block

prbsix = prb2(1:(6*2048),:,:);

% extract eight second block

prbeight = prb2((6*2048+1):end,:,:);

% grow six second block into eight second block

prbsix = [ prbsix ; zeros(2*2048,size(prbsix,2),size(prbsix,3))];

% stack the repitions on top of each other

prbeight = reshape(prbeight,[],3);

prbsix = reshape(prbsix,[],3);

If i am not wrong the summary of code is as follows:

The summary of this code is that it takes a signal of 140s and then it divides it into parts of 14 seconds ,then it splits the 14 seconds into parts of 6s and 8s. Then it takes the 1st 6s and store it in a variable and makes it 8s, After that it takes the 8s and stores it in another variable.The code then repeat this procedure for the total of 140 seconds and adds the values of next 6s to the variable declared for 6 seconds and similarly does this for 8s to the end of the signal.