# How do I create a matrix that has as values ​​the averages of variables found in loops?

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Agnese Chini on 25 Sep 2021
Commented: Agnese Chini on 25 Sep 2021
My program analyzes a reference image: named '21', then cut out two ROIs from this image and save their coordinates. Then to the remaining images cut out the same number of ROIs at the same coordinates.
At the end of the program I will have 2*21=42 ROIs.
srcFile = dir('C:\Users\agnes\Pictures\pp4 tgc-med rd20\*.dcm');
pathname = ('C:\Users\agnes\Pictures\pp4 tgc-med rd20\');
% define these image
numberofimages = 21;
numberofroi = 2;
% show the reference image
imshow(I)
% use imcrop to get rectangle coordinates
R = zeros(numberofroi,4);
for nr = 1:numberofroi
[~,R(nr,:)] = imcrop(gca);
end
% crop corresponding ROIs from each non-reference image
for ni = 1:numberofimages
for nr = 1:numberofroi
filename=(num2str(ni));
info=dicominfo(strcat(pathname,filename));
end
end
% show the cropped image regions for demonstration
For these ROIs I have to compute the mean and save the result in a 21*2 matrix, who can I do that?

Matt J on 25 Sep 2021
Edited: Matt J on 25 Sep 2021
If that's all you want to do, you shouldn't be saving the coordinates of the ROIs. You should just create a binary mask BW of each ROI and stack your images in a 3D stack A and do
sum(A.*BW,[1,2])./sum(BW,[1,2]);
Agnese Chini on 25 Sep 2021
Thank you very much for helping. From the obtained matrix is ​​there a way to know when the values ​​repeat?
For example, if in the first column and first row I have the value x, when does it appear in another position?

R2020b

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