about dynamic variable name for output

Hi there, In the code below I want dynamic outputs for 'k' value in the loop. For instance if c=2 I want to get region_number1,region_number2,locs1, locs2 for the output. How can I do this?

for k=1:c
    [region_number,locs]=find_region_pixels(first_order_big(:,:,k),orig_image);
end

[Stephen23]

While it is possible, creating dynamic variable names will make your code slow and buggy:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Learn to use indexing, which is fast, simple, and reliable:

 region_number = NaN(1,c);
 locs = NaN(1,c);
 for k = 1:c
    [region_number(k),locs(k)] = find_region_pixels(first_order_big(:,:,k),orig_image);
end

Change the output size and/or class (e.g. cell array) to suit the outputs of that function.

[Huseyin]

first_order_big has multidimensional data inside. So this code gives me an error like: "In an assignment A(:) = B, the number of elements in A and B must be the same."

How can I fix this?

[Walter Roberson]

 region_number = NaN(1, c);
 locs = cell(1, c);
 for k = 1:c
    [region_number(k),locs{k}] = find_region_pixels(first_order_big(:,:,k),orig_image);
  end

Answer 1

[Stephen23]

https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

[Jan]

100 votes from me.

@Mathworks: Please let this answer appear whenever a user types the terms "dynamic" and "variable" in one sentence.

Answer 2

[Image Analyst]

Yes, you can use regionprops, which will measure those things. Then put the results into a cell array:

for k = 1 : numberOfImages
    thisLabeledImage = first_order_big(:,:,k);
    % Ask for PixelList, which is a list of all (x,y) points that are white/true/1 in the labeled image.
    props = regionprops(thisLabeledImage ,orig_image, 'PixelList');
    % There may be more than one blob in the image, so props is a structure array.
    % For this image, just store this image's blobs' coordinates into a cell array for use later.
    blobPixels{k} = props(k);
end