Re: Please, help me vectorize this code

[michele]

On 09/17/2017 01:15 PM, Pablo Fernández Bustamante wrote:
> Hi,
>
> I want the elements of a matrix M_ to be equal to those of an original 
> matrix M but only if they satisfy a certain condition, otherwise write 
> a zero.
>
> The following lines of code work as expected but I want to avoid the
> loop if it is possible.
>
> >> M = floor(rand(5, 4)*10);
> >> [r, c] = find(M > 4);
> >> M_ = zeros(5, 4);
> >> for n = 1:length(r)
> M_(r(n), c(n)) = M(r(n), c(n));
> endfor
>
> I have tried
>
> M_ = M(find(M>4));
>
> but that returns a column vector of the elements which satisfy the 
> condition.
>
> Thanks in advance,
>
> Pablo
>
>
>
>
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You can do like this:

M = floor(rand(5,4)*10);
M1 = zeros(5,4);
M1(M>4) = M(M>4);

Bests,

--
Michele Ginesi