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Re: check if a square matrix is diagonal

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115300] Re: check if a square matrix is diagonal
  • From: "lumeng.dev at gmail.com" <lumeng.dev at gmail.com>
  • Date: Fri, 7 Jan 2011 04:07:59 -0500 (EST)

 d == Dimensions[m];

should be changed to

 d == Dimensions[m][[1]];

Also you need to check if m is square before computing a mtemp, for example,
do

SameQ @@ Dimensions[m]


On Thu, Jan 6, 2011 at 01:06, benyaya <xiaochu at gmail.com> wrote:

> What I try to do is extract the diagonal, subtract if from the matrix,
> then compare the new matrix with 0.
> My code doesn't work out though, can anyone help? thanks a lot.
>
> checkIfDiagonalMatrix[m_] == Module[{d, mtemp},
>  d == Dimensions[m];
>  mtemp == DiagonalMatrix[Diagonal[m]] - m;
>  If[mtemp == Table[Table[0, {i, 1, d}], {i, 1, d}],
>   True,
>   False]
>  ]
>
>

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Meng Lu (=E9=99=86=E8=90=8C)
(+1) 614-312-4902
fax: +1-217-398-0747


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