Combining two for loops into a nested loop

Suppose I have a forloop that yields a 1x3 output

for i = [1:3] % 3 months

mdl = fitlm(X((30*i-30+1):i*30,:),Y((30*i-30+1):i*30,3)) % regression

% for one month of the regressors X on Y for stock 1.

montherrors(:,i) = mdl.Residuals(:,1) % isolate the daily errors

errors = table2array(montherrors) % convert to array so I can perform

% calculations

stdev = std(errors, 1)

idio_three = stdev * sqrt(ndays) % so obtain 3 monthly idio-risks

end

And another loop that also yields a 1x3 output

i = 1 % so no loop over i

for j = [1:3] % 3 months

mdl = fitlm(X((30*i-30+1):i*30,:),Y((30*i-30+1):i*30,j)) % regression

% for one month of the regressors X on Y for stock 1.

montherrors(:,j) = mdl.Residuals(:,1) % isolate the daily errors

errors = table2array(montherrors) % convert to array so I can perform

% calculations

stdev = std(errors, 1)

idio_j = stdev * sqrt(ndays) % so obtain 3 monthly idio-risks

end

Now I would like to combine the two to obtain a 3x3 matrix output. I have tried multiple strategies but cant seem to figure it out.

I tried

for j = [1:3] % number of stocks 1 , 2 and 3

for i = [1:3] % 30*180 = 5400 days

mdl = fitlm(X((30*i-30+1):i*30,:),Y((30*i-30+1):i*30,j)) % regression

% for one month of the regressors X on Y for stock 1.

montherrors(:,(i*j)) = mdl.Residuals(:,1) % daily errors for

errors = table2array(montherrors) % convert to array so I can perform

% calculations

stdev = std(errors, 1)

idio_one(j,:) = stdev * sqrt(ndays) % so obtain 3 monthly idio-risks

end

end

But then i get the error Cannot create a table variable with a discontiguous index.

Answer 1

[MJFcoNaN]

Please check whether this step is correct:

montherrors(:,(i*j)) = mdl.Residuals(:,1)

Maybe you need one of these:

%(1)
montherrors(:,(i)) = mdl.Residuals(:,1)
% or (2)
count = 0;
for j = [1:3] % number of stocks 1 , 2 and 3
    for i = [1:3]
        count=count+1;
        % ...
        montherrors(:, count) = mdl.Residuals(:,1)
        % ...
    end
end

[Wietze Zijpp]

I had tried

montherrors(:,(i*j)) = mdl.Residuals(:,1)

But that gives the error: Cannot create a table variable with a discontiguous index.

When using your proposed count the loop acttually works !!

Thank you for your help