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Re: Weird behavior of SparseArray


$Version
5.1 for Microsoft Windows (October 25, 2004)

Hi Adel,
in this version it seems to work o.k.
On the other hand, I saw problems with sparse matrixes in numeric 
routines, but I did not report them.

sincerely, Daniel

Adel Elsabbagh wrote:
> Dear all
> 
> I don't understand what is going on with SparseArray
> 
> If I write this:
> 
> cp1 = SparseArray[{i_, j_} -> 0, {4, 2}];
> cp1[[Range[4], 1]] = cp1[[Range[4], 1]] + {1, 1, 1, 1};
> cp1 // MatrixForm
> 
> I get cp1 with all entries equal to zero
> 
> However, if use Table instead of SparseArray I get the right answer.
> 
> More surprisingly, if I write this: 
> 
> cp1 = SparseArray[{i_, j_} -> 0, {4, 2}];
> cp1[[Range[4], 1]] = cp1[[Range[4], 1]] + {1, 1, 1, 1};
> cp1 // MatrixForm
> cp1[[Range[4], 1]] = cp1[[Range[4], 1]] + {1, 1, 1, 1};
> cp1 // MatrixForm
> 
> I get ones in the first column!!
> 
> Any explanation?
> 


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