How to calculate a 3D-array-matrix?

Hello,

I would like to calculate a matrix which should be consists out of three dimensions. Lets be R_m_boot(i,:) a ix1000 matrix. I´ve tried the write following code, but it doesn´t work.

for l=1:1:length(z_boot);

        mu(i,:) = R_m_boot;
        sigma_R_m_boot(i,l) = (std(z_boot(:,l))/(sqrt(N)));

        % First trial 
        f_norm = (normpdf(z(:,l),mu(i,l),sigma_R_m_boot(i,l)))';
        f_normal = [f_normal; f_norm];

        --> but: how can I get the 3.rd dimension (parameter i)

        % Second trial
        f(l,:,i)=(normpdf(z(:,l),mu(i,l),sigma_R_m_boot(i,l)));
    end

Can somebody help me, please?

[Vaclav Rimal]

Have you tried preallocating your resulting matrix first?