how do I put arrays into a for loop

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studentmatlaber 2021-4-15

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评论： Rik 2021-4-23

I have a .mat file. There are 24 array in this file. I want to calculate the mean of the first N elements of an array.

But what I want is for the 24 directories in the .mat file to automatically enter this into a for loop. I am waiting for your help in this matter.

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Stephen23 2021-4-15

编辑：Stephen23 2021-4-15

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"There are 24 array in this file. Array names like y1, y2 ... "

The most important thing is to load into an output variable:

S = load(...);

then you can trivially access the fieldnames of the structure S:

https://www.mathworks.com/help/matlab/ref/fieldnames.html

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

Loop over the fieldnames, allocate the data to an array, perform your calculation on the array. Done.

Rik 2021-4-23

Backup of this question:

how do I put arrays into a for loop

I have a .mat file. There are 24 array in this file. I want to calculate the mean of the first N elements of an array.

But what I want is for the 24 directories in the .mat file to automatically enter this into a for loop. I am waiting for your help in this matter.

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SungJun Cho 2021-4-15

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编辑：SungJun Cho 2021-4-15

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To calculate the mean of the first N elements of an array, you can use

mean_y1 = mean(y1(1:N));

However, you may import a .mat file which I suppose will give you a matrix in which each row or column is one array. In that case, just perform

mean_mat = mean(Y(:,1:N),2); % if each row is an array
mean_mat = mean(Y(1:N,:),1); % if each column is an array

and you will get a matrix containing the mean of first N elements of each array.

This should be a more efficient way to compute the mean than to use a for loop, but if using a for-loop is necessary, feel free to let me know.

I imported your data as a structure type, then converted it into a cell type using "struct2cell". Once the data was converted, I noticed that the arrays named "y" (e.g., y1, y10, etc.) were located from 30th to 53rd rows of the data, so I extracted only those arrays so that the variable "Y" contains only the y arrays.

studentmatlaber 2021-4-15