Re: bsxfun and sparse matrices in Matlab

[PhilipNienhuis]

Jordi Gutiérrez Hermoso-2 wrote:
> 
> While testing more things about auto BSX, I noticed that I missed to
> overload the operators for sparse matrices, and while investigating
> *that*, it seems like bsxfun destroys sparsity. While this may make
> sense for some operators (e.g. power operators), I wanted to confirm
> if this is what Matlab does.
> 
> Can someone please confirm if the following does not produce sparse
> matrices?
> 
>     x = sprand(1,3,1/3); y = x';
>     bsxfun(@plus, x, y)
>     bsxfun(@minus, x, y)
>     bsxfun(@times, x, y)
>     bsxfun(@rdivide, x, y)
>     bsxfun(@ldivide, x, y)
>     bsxfun(@power, x, y)
> 
> 

At work (ML r2009a):

>> x = sprand(1,3,1/3); y = x'
y =
   (3,1)       0.1270
>> issparse (bsxfun(@plus, x, y)
ans =
     1
>> issparse (bsxfun(@minus, x, y))
ans =
     1
>> issparse (bsxfun(@times, x, y))
ans =
     1
>> issparse (bsxfun(@rdivide, x, y))
ans =
     1
>> issparse (bsxfun(@ldivide, x, y))
ans =
     1
>> issparse (bsxfun(@power, x, y))
ans =
     1

(empty lines removed)


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