Extract sub-matrix compute correlation coefficient 2D case iteratively

Hello friends, I will like to extract 2x2 sub-matrices from a large matrix and calculate correlation coefficient for each of the 2x2. Loop the procedure over the main matrix and store the correlation coefficient in output file. the for loop gave some error, I will appreciate guide to fix the code. Thank you.

% infile
file1='d.dat';   %
file2='b.dat';   %

% Outfile
correlout='correl.dat';  %

numcols=20;           % 
numrows=20;
%open file
fid1=fopen(file1);
f1=fscanf(fid1,'%f',[numcols numrows]);    
fclose(fid1);

fid2=fopen(file2);
f2=fscanf(fid2,'%f',[numcols numrows]);  
fclose(fid2);
%reshape
Refid1=reshape(fid1,[numcols,numrows]);
Refid2=reshape(fid2,[numcols,numrows]);

%pre-allocate
ccoef=zeros(numrows,numcols);
cRes=zeros(numrows,numcols);
subf1(i)=zeros();
subf2(i)=zeros();
%loop over 
for i=1:numcols
    for j=1:numrows
      subf1(i) = Refid1(i:i+1, j:j+1);
        subf2(i) = Refid2(i:i+1, j:j+1);
        ccoef(i)=corrcoef(subf1(i),subf2(i));
      cRes(i)=ccoef(1,2);
    end
end
%outfile
correlout=cRes(i);
%write to file
fid=fopen(correlout, 'w');
fprintf(fid,'%6.2f\n',correlout);
fclose(fid);

Answer 1

[darova]

• Sometimes i+1 > numcols. What will happen then? (RED)
• Left side has one number, right one - 4. (GREEN)

[darova]

Why replacing sizes?

[Joshua]

Thanks for the observation I will update it. How best can this be allocated to prevent i+1> numcols

subf1(i)=Refid1(i:i+1,j:j+1);
subf2(i)=Refid2(i:i+1,j:j+1);

[darova]

[darova]

[Joshua]

Many thanks. The loop works but cannot write to output file. Any suggestion on this please.

[darova]