How to map elements?

Hello everybody,

I am cleaning some code and I came across with the following and I hope you guys can give some extra insigths.

The code is working like shown but I'd like to simplify it somehow.

• Both hil and rom are allocated.
• schema contains indexes. The value of these indexes is no greater than the dimensions of hil and rom.
• hil initially is zeros and I want to fulfill it with values from rom in due position.

for i = 1:M
        for j = 1:N
            hil(i,schema(i,:,j),j) = rom(i,schema(i,:,j),j); 
        end
    end

Thanks,

Rui

Answer 1

[Matt J]

I think your current approach is optimum.

The only exception is if you're going to repeat this for different rom, but the same schema. Then I would do

    [ii,jj]=ndgrid(1:N);
    ss=scheme(1:N,:,1:N);
    idx=sub2ind(size(rom),ii(:),ss(:),jj(:) );

and now you can repeatedly do

      hil(idx)=rom(idx)

reusing idx for different rom.

Answer 2

[Rui]

Thanks Matt. In my case I am not able to redefine the number of elements on any dimension (if just 1 dimension could be redimensioned, we could get rid off 1 cycle, and so on), so I suppose I will have to live with that.

Cheers, Rui