You do not say how rowspan and colspan are calculated, but the problem is that they do not match the size of R1 (or the other two arrays, probably). The solution depends on what you want. If rowspan and colspan are correct but you do not want the whole of R1, try
C(rowspan,colspan,1) = R1(rowspan, colspan);
% etc
assuming R1 is a 2-D matrix and rowspan and colspan represent a part of it.
If you want the whole of R1 etc. you can use
rowspan = 1:size(R1, 1);
colspan = 1:size(R2, 2);
to get the correct ranges.
