MATLAB: How to populate an array dynamically

building arrays

It's a little hard to describe exactly what I'm trying to do, but the code below should make it clear. Basically I'm trying to populate an array with elements from another array, with the elements specified dynamically. The closest I've been able to come is the code below. I know it's best to avoid Eval, so if someone has a better, more elegant solution I'd love to hear it. I'm very new to Matlab, so I'm probably missing something easy. Thanks, J.C.
totalValue = rand(1, 10);
startSegmentEval = [1, 2, 3, 4, 5];
endSegmentEval = [3, 4, 5, 6, 7];
A = 'sum(totalValue(';
B = ':';
C = ')';
D = int2str(startSegmentEval');
E = int2str(endSegmentEval');
F = ';';
temp = [repmat(A, numel(D), 1), D, repmat(B, numel(D), 1), E, ...
       repmat(C, numel(D), 1), repmat(C, numel(D), 1)];
a(1:5) = eval(temp);

Best Answer

Your temp is this:
temp =
sum(totalValue(1:3))
sum(totalValue(2:4))
sum(totalValue(3:5))
sum(totalValue(4:6))
sum(totalValue(5:7))
yet totalValue is a 2D array, not a 1D array. Can you explain what you're doing? Are you using linear indexing?
Secondly, whatever you're doing, summing values like that is not a normal, or intuitive way to do it. You'd better off just using a for loop, or a vectorized function like conv(). I could suggest code to do it with conv() if it made more sense what elements you wanted to sum in the 2D array totalValue.
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