Indexing and replacing value in a zero matrix based on a table

Hello,

I am trying to input a value in a zeros matrix of size 11*10. This is based on a variable which has three columns (Number, ID, ANS) as shown below. Now I want to insert the value in ANS which is -1 in the zeros matrix at 10x5 (ID x Number) position (index). Any suggestion on how this can be done?

Number ID ANS

5 10 -1

Answer 1

[Walter Roberson]

If your Number and ID and ANS are scalar then

YourMatrix(Number, ID) = ANS;

If they are vectors then there are multiple approaches, including:

YourMatrix( sub2ind(size(YourMatrix), Number(:), ID(:)) ) = ANS(:);

Or

YourMatrix = YourMatrix + accumarray( Number(:), ID(:), ANS(:), size(YourMatrix) );

and there are approaches using sparse.

Answer 2

[Arvind Sathyanarayanan]

Is this what you're looking for?

ID = 10; Number = 5; Ans = -1;
tmat = zeros(11,10);
tmat(ID,Number)=Ans;