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MathGroup Archive 2005

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Re: Weird behavior of SparseArray

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58400] Re: Weird behavior of SparseArray
  • From: dh <dh at metrohm.ch>
  • Date: Thu, 30 Jun 2005 06:16:02 -0400 (EDT)
  • References: <da0bek$fjr$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

$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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