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Re: fast replace for matrix minor


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


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