I understand, you want to append an additional matrix as a variable in multiple MAT-files automatically. I assume you have multiple MAT-files created already. First of all, I recommend saving these files in a single directory.
Once done, kindly refer the below script.
matfiles = dir('<filepath>\*.mat'); %e.g. dir('C:\Users\*.mat')
x = zeros(512,512); %512-by-512 null matrix
N = length(matfiles) ;
for i = 1:N
save(matfiles(i).name, 'x', '-append')
end
This should append the variable 'x' to all the MAT-files in present your directory.
