MATLAB: How to get Cumulative sum of elements based on negative sign

sum of elements based on sign

I have 2 vectors >> z=1:9; >> l=[1 2 -3 4 -5 6 7-8 9 10] starting from last element of l i.e 10 9….1 check for 1st negative element i.e. l=-8 if l=-8 add z8+z9 check for next negative element i.e l=-5 if l=-5 add z5+z6+z7 (elements between two negative numbers -5 and -8) check for next negative element i.e l=-3 add z3+z4 and add z1+z2 finally i should get new vector w=[z1+z2, z3+z4,z5+z6+z7,z8+z9]

Best Answer

Your array l has one more element than z. why? Anyway,
z = 1:9;
l = [1 2 -3 4 -5 6 7 -8 9];
negposition = find(l < 0);
w = arrayfun(@(s, e) sum(z(s:e)), [1 negposition], [negposition-1 numel(z)])
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