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Re: It would be nice to have DiagonalMatrix accept a matrix as building

  • To: mathgroup at smc.vnet.net
  • Subject: [mg113536] Re: It would be nice to have DiagonalMatrix accept a matrix as building
  • From: "Nasser M. Abbasi" <nma at 12000.org>
  • Date: Mon, 1 Nov 2010 05:02:27 -0500 (EST)

On 10/31/2010 6:47 AM, Patrick Scheibe wrote:
> Hi,
>
> aehmm, what about
>
> SparseArray[Band[{1, 1}] ->  {b,b,b,b,b,b}]
>
> where b={{1, 2}, {3, 4}}?
> Takes me about 5 seconds to type. So why care that DiagonalMatrix
> can't do it?
>
> Cheers
> Patrick
>

Well, if you wanted to repeat the block 200 times, you probably do not 
want to sit and type 'b' 200 times :)

But using ConstantArray, like Zach just mentioned is what I did not know 
about.  His solution:

SparseArray[Band[{1, 1}] -> ConstantArray[block, {nBlocks}]]

is good enough so not to require special option for DiagonalMatrix. So 
this issue is closed for me. I'll use ConstantArray for this.

Thanks for everyone input on this.

--Nasser


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