Weird behavior of SparseArray
- To: mathgroup at smc.vnet.net
- Subject: [mg58387] Weird behavior of SparseArray
- From: Adel Elsabbagh <aelsabbagh at gmail.com>
- Date: Thu, 30 Jun 2005 04:37:22 -0400 (EDT)
- Reply-to: Adel Elsabbagh <aelsabbagh at gmail.com>
- Sender: owner-wri-mathgroup at wolfram.com
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?
--
Adel