Re: sparse matrix question

• To: mathgroup at smc.vnet.net
• Subject: [mg56162] Re: [mg56128] sparse matrix question
• From: DrBob <drbob at bigfoot.com>
• Date: Sun, 17 Apr 2005 03:07:10 -0400 (EDT)
• References: <d3lrsq\$sef\$1@smc.vnet.net> <200504150847.EAA11518@smc.vnet.net> <200504160752.DAA24641@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```l={{a,b},{c,d},{e,f}};
p={3,4,6};
SparseArray@
Flatten[Transpose[{p,l}]/.{a_Integer,{b_,c_}}\[RuleDelayed]{Rule[{1,a},b],\
Rule[{2,a},c]}]

SparseArray[<\[InvisibleSpace]6\[InvisibleSpace]>,{2,6}]

Normal@%

{{0,0,a,c,0,e},{0,0,b,d,0,f}}

%[[All,3]]

{a,b}

Bobby

On Sat, 16 Apr 2005 03:52:10 -0400 (EDT), Ted Sariyski <tsariysk at craft-tech.com> wrote:

> Hi,
>
> I have a list
> l={{a,b},{c,d},{e,f}}
> and a list of pointers  to the non-zero columns of a
> sparse matrix e.g. p={3,4,6}:
>      | 0 0 a c 0 d 0 ... |
> m=    |                   |
>       | 0 0 b d 0 e 0 ... |
>
> What is the best way to do this? How can I address a column in
> mathematica?
>
> Thanks,
> Ted
>
>
>
>
>
>
>

--
DrBob at bigfoot.com

```

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