What wrong with the indexing code?

If I want to fill in a matrix, of which I have its indices without a for loop, how could I do it? Suppose that the (row(i),col(i)) elements to be filled are given.

value = 189;
row = [  1 3 6 7 8 ];
col = [ 1 1 4 4 5];
B(row,col) = value

Answer 1

[Walter Roberson]

B = full( sparse(row, col, value) );

or

B = accumarray([row(:), col(:)], value);

[GEORGIOS BEKAS]

how about using arrayfun/bsxfun or something?

[Walter Roberson]

Not at all easily with arrayfun or bsxfun as assignment through function calls is difficult and never less than ugly.

Answer 2

[Birdman]

B(sub2ind([max(row) max(col)],row,col)) = value

[GEORGIOS BEKAS]

as usual; can you explain that?

[Birdman]

sub2ind function converts the equivalent indexes of given rows and columns and it should also know the size of your matrix. The inputs are accordingly given. For instance, the linear index representation for a matrix having 2 rows and 5 columns, the index of the element at

row=2;
col=3;

is

 6

[GEORGIOS BEKAS]

It does not solve the problem. I want B(row(i), col(i)) = value, without using a for loop.

[Birdman]

I did not use for loop here,as you can see.

[GEORGIOS BEKAS]

   sz = [max(row), max(col)]
    B(sub2ind(sz, row, col)) = value
    B = reshape(B, sz)

[Walter Roberson]

The reshape() is not needed.

[Birdman]

Doesn't my answer also work Walter?

[GEORGIOS BEKAS]

it did not :/