how do I put arrays into a for loop
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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.
2 个评论
"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:
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.
采纳的回答
SungJun Cho
2021-4-15
编辑：SungJun Cho
2021-4-15
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.
9 个评论
studentmatlaber
2021-4-15
SungJun Cho
2021-4-15
Can you provide your .mat file so that I can take a look at it?
Jan
2021-4-15
" the arrays I have are not in a matrix." - This is the main problem. If thevariables are store in a matrix, the processing is trivial. So this is the solution: Store the data in arrays.
studentmatlaber
2021-4-15
SungJun Cho
2021-4-15
You can try clicking "Insert" and attach your .mat file in the comment.
SungJun Cho
2021-4-15
As Jan mentioned, it is best to store the variables in matrix for convenience. For now, you can do
data_path = '../Downloads/Data_x30_y30_28.mat'; % change this path to where your data is located
data = struct2cell(load(data_path));
data = data(30:53); % select y arrays
Y = cat(1,data{:}); % storing data into a matrix format
mean_mat = mean(Y(:,1:N),2); % given each row is an array
I believe this will solve your problem for now.
studentmatlaber
2021-4-15
SungJun Cho
2021-4-15
No problem!
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
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