How do I create a simple loop to sum up the elements in my matrix assuming some elements vary.

Tp1 = [ E*A1 E*Sx1 E*Sy1 E*Sw1 ; E*Sx1 E*Ix1 E*Ixy E*Iwy; E*Sy1 E*Ixy E*Iy1 E*Iwx ];

To1 = [ 0 0 0 0; 0 0 0 0; 0 0 0 0] ;

Kt1=repmat({Tp1},128,128);

Kt1([28,48,50,124])={To1};

Kt1=cell2mat(Kt1);

Answer 1

[Dave B]

You don't need a loop:

a = rand(3,4)

a = 3×4

0.2467 0.9178 0.3863 0.5492 0.8022 0.1494 0.9996 0.6980 0.3715 0.9611 0.1072 0.4959

sum(a) % sum of each column, also sum(a,1)

ans = 1×4

1.4204 2.0283 1.4931 1.7431

sum(a,2) % sum of each row

ans = 3×1

2.1000 2.6492 1.9356

sum(a,'all') % sum of all values, or sum(a(:)) on old releases

ans = 6.6848

If you really want to do it in a loop:

s=0;
for i = 1:numel(a)
    s=s+a(i);
end
s

s = 6.6848