Asked by Uerm
on 10 Oct 2019

Hi,

I have a variable X which is a 1x48 cell containing matrices of sizes Ax128. The number of A differs between the matrices. Basically, I want to calculate the derivative of each matrix individually along each row. How can I do that? If say, one of the matrices is 34x128, the end result of this matrix should be 34x127.

Answer by Stephen Cobeldick
on 10 Oct 2019

Edited by Stephen Cobeldick
on 10 Oct 2019

Accepted Answer

fun = @(m)diff(m,1,2);

out = cellfun(fun,X,'uni',0);

Answer by Uerm
on 10 Oct 2019

Edited by Uerm
on 10 Oct 2019

Thanks for the help! I have an additional question:

I have a variable y1, which is also a 1x48 cell. Each of these cells is a vector. y1 is a variable for ECG signals with 48 different patients/subjects.

The variable X from the initial question (1x48 cell with Ax128 matrices) contains segments. These segments should be applied to the ECG signal for each patient to segment the ECG signal.

Say X{1,1} is a 34x128 matrix and the first row (of the first matrix) of X has start and end values X{1,1}(1,1) = 370 and X{1,1}(1,end) = 37499

The first segment of the signal (first row of the first matrix) will therefore be y1{1,1}(X{1,1}(1,1):X{1,1}(1,end)). However, this should be done for each row and each patient. How can I do that?

Answer by Uerm
on 14 Oct 2019

Edited by Uerm
on 14 Oct 2019

Well, sort of. I attach some screenshots of the variables and their content to make it easier to understand.

As you can see on image 1, y1 is a 1x48 cell each containing a 1x650000 double. Data_128 contains the R peaks of the ECGs in segments. So Data_128{1,1} is a 34x128 matrix - 34 segments of R peaks each containing 128 R peaks. I want to "segment" y1 based on the values in Data_128. So for patient 1, y1{1,1} should be divided in 34 segments. For patient 2 (y{1,2}), it is 28 segments etc. The first segment of y1{1,1} should be (in samples) [1:37499]. The second will be [19080:55908]. The third [37782:74473] etc. (basically from start of segment to end of segment). This should be done for all 48 patients. Hope the explanation helps.

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