symsum undefined error for input arguments

Question

Margherita Premoli 2020-3-5

回答： Steven Lord 2020-3-5

Hi, I need to sum the variable Dmet(b,t) over b, which varies from 1 to b-1.

The variable Dmet is the demand met at a certain day t with a certain batch b so Dmet is defined by two indices.

I tried to formulate it but it is not working, can anyone help me out? Thanks!!

This is part of the code:

syms b

D= 10

for t=1

for b=1:3

Dmet(1,t)=3

Dmet(2,t)=4

Dmet(3,t)= D - symsum(Dmet(b,t),b,1,b-1)

end

Do I have to use a syms diffferent than b?

Answer 1

Steven Lord 2020-3-5

Your b variable isn't symbolic at the time you try to use it in symsum. It was overwritten by the loop variable for your inner loop.

But even if it wasn't, symsum isn't the right tool for this job. Use sum instead.

A = reshape(1:16, 4, 4)
sum(A(:, 1:3), 2)