How to keep a matrix from rewriting every loop iteration?

Hi guys, I'm having a problem with assigning values form a matrix to another matrix using loop functions.

Here is the code:

 for t=1:Nw
    for i=1:Nh
    eN=Am(t:t+1,i:i+1)
    nEN=reshape(eN',1,[])
      for i1=1:4
      KG=[];
      KG(nEN((2*i)-1),nEN((2*i)-1))=Ke(2*i1-1,2*i1-1)
      KG(nEN(2*i),nEN(2*i)=Ke((2*i1),(2*i1))
      end
    end
 end

'KG' is a matrix with known amount of rows and columns and was initially filled with zeros. 'Ke' is a 8x8 matrix with constant values. 'nEN' is returned as an array of 4 numbers.

The problem is that for every iteration previously calculated values are set to zero and as a result I get a matrix with only two values calculated in the last iteration, whether I need a complete matrix filled fully with values from each iteration. I know I can prevent the matrix from being rewritten every time, but I don't remember how. Can anyone help? Thanks.

[Vitaly]

Omitting KG = [] before the loop works, thanks to Jan Simon, however the arrays nEN can have values that are the same for some iterations, and I need the corresponding values in Ke to add up in KG if that happens, but now it's just replacing the values if they're the same.

So the question now is how to make the function to add up new values to already existing ones in KG instead of replacing them?

Answer 1

[Jan]

What about simply omitting

KG = []

?

[Vitaly]

I have it in line 6, or you mean put it in the statements in lines 7-8?

[Vitaly]

I've put it before the loop and it seems to be working now...thanks

[Vitaly]

the arrays nEN can have values that are the same for some iterations, and I need the corresponding values in Ke to add up in KG if that happens, but now it's just replacing the values if they're the same. do you know how I can deal with this?

[Vitaly]

the question now is how to make the function to add up new values to already existing ones in KG instead of replacing them?

[Jan]

KG(index) = KG(index) + newValue