MATLAB using 2D Array - arrays

Question

i want to use a 2D array to store all the values of img1, img2 and the compared vlaue of img1 and img2,
I want to achive the algorithm likes:
% read in the images from a folder one by one:
somefolder = 'folder';
filelist = dir([somefolder '/*.jpg']);
s=numel(filelist);
C = cell(length(filelist), 1);
for k=1:s
C{k}=imread([somefolder filelist(k).name]);
end
%choose any of the two images to compare
for t=1:(s-1)
for r=(t+1):s
img1=C{r};
img2=C{t};
ssim_value[num][1]=img1; % first img
ssim_value[num][2]=img2; % second img
ssim_value[num][3]=mssim; % ssim value of these two images
end
end
So, there is error about using the 2D array (ssim_value) that I used, what is the correct way of initialization it, and how to achieve the purpose that save the values that I want to store.
Could someone help me. Thanks in advance.

Answer 1

I'm assuming that "num" is a number that you will supply, like 5 or something. You cannot mix types in arrays as you do in Python. Also, as #Schorsch pointed out, you use parenthesis to index arrays in Matlab.
The two-dimensional array you are trying to form needs to be a 2-D cell array. For example:
a = {{"a",3},{"two",[1,2,3]};
In this case, a{1,2} = 3, and a{2,1} = "two".
You may not know in advance how many files are in the directory, so pre-initializing the cell array may not be possible in advance. In any case, Matlab arrays only need to be pre-initialized for performance reasons, and you can easily find information on initializing arrays in Matlab.
In light of this, I'm pretty sure what you are trying to accomplish is:
%choose any of the two images to compare
ssim_value = {};
for t=1:(s-1)
for r=(t+1):s
img1=C{r};
img2=C{t};
ssim_value{num,1}=img1; % first img
ssim_value{num,2}=img2; % second img
ssim_value{num,3}=mssim; % ssim value of these two images
end
end