Re: Assigning elements to a matrix

• To: mathgroup at smc.vnet.net
• Subject: [mg47381] Re: Assigning elements to a matrix
• From: "Gareth J. Russell" <gjr2008 at columbia.edu>
• Date: Wed, 7 Apr 2004 03:16:42 -0400 (EDT)
• Organization: Columbia University
• References: <c4u3ko\$9lq\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In <c4u3ko\$9lq\$1 at smc.vnet.net> Mark Coleman  wrote:
> Greetings,
>
> I need to create a series of n x n matrices, in both conventional and
> sparse matrix formats. I have a (large) table of lists, where each
> list  is of the form:
>
> {i,j,value}, where {i,j} are the row-column indices and value is the
> corresponding numerical value, i.e., m[[i,j]]=value.
>
> Using this data I need to create an n x n matrix where all the values
> except those specified in my list are 0. I would also like to create a
> similar matrix, this time using Mathematica's built-in SpareMatrix
> format.
>
> Can anyone suggest a way to do this?
>
> Thanks,
>
> -mark

Mark,

Have you looked at the documentation for SparseArray? If you convert
each list from {i,j,value} to {{i,j}->value} and send the resulting
table to SparseArray, you've done it.

Normal[mySparseArray] give you the full array equivalent.

It's all in the Help Browser...

Gareth Russell

Columbia University

```

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