Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

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>
  • Reply-to: drbob at bigfoot.com
  • 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


  • Prev by Date: Re: sparse matrix question
  • Next by Date: How can I get a nonscalar logical variable into a compiled function?
  • Previous by thread: sparse matrix question
  • Next by thread: Re: sparse matrix question