Groups > comp.soft-sys.math.mathematica > #3292

Re: Replacement rules for large matrixes

From	dr DanW <dmaxwarren@gmail.com>
Newsgroups	comp.soft-sys.math.mathematica
Subject	Re: Replacement rules for large matrixes
Date	2011-06-25 09:27 +0000
Organization	Steven M. Christensen and Associates, Inc and MathTensor, Inc.
Message-ID	<iu49mi$jmf$1@smc.vnet.net> (permalink)

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Is your matrix a nested list or a SparseArray[]?  From your description, I am guessing it is a nested list.  Try working with your matrix as a SparseArray[] instead.

Next problem: Replace[] does not work on SparseArray[]'s.  However, you can use BlockRules[] (code below) to do the replacement.

Code for BlockRules[] by Andrew Moylen at Wolfram, from an earlier posting on this group that I can't find right now:

SetAttributes[BlockRules, HoldRest]; 

BlockRules[rules_, expr_] := Block @@ Append[Apply[Set, Hold[rules], {2}], 
    Unevaluated[expr]]

Enjoy,
Daniel

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Re: Replacement rules for large matrixes dr DanW <dmaxwarren@gmail.com> - 2011-06-25 09:27 +0000

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