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Re: fast replace for matrix minor

• To: mathgroup at smc.vnet.net
• Subject: [mg69515] Re: [mg69476] fast replace for matrix minor
• From: "Carl K. Woll" <carlw at wolfram.com>
• Date: Thu, 14 Sep 2006 06:56:43 -0400 (EDT)
• References: <200609130803.EAA18423@smc.vnet.net>

Christopher Arthur wrote:
> Is there a quick way to replace a small minor block in a large matrix? 
> Using ReplacePart in a Do loop seems to be very inefficient with 
> respect to timing
> 
> Chris Arthur

Something like this?

m=Array[Plus,{5,5}];

Replace minor block with rows 2,3,4 and columns 4 and 5:

m[[Range[2,4],Range[4,5]]] = {{a,b},{c,d},{e,f}};

Now, the matrix m has had a minor block replaced with the above matrix.

Carl Woll
Wolfram Research

• References:
  • fast replace for matrix minor
    • From: Christopher Arthur <caa0012@unt.edu>