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Re: Determinant of a matrix [message #86574 is a reply to message #86569]

Wed, 20 November 2013 05:37

lecacheux.alain
Messages: 325
Registered: January 2008

Senior Member

Le mercredi 20 novembre 2013 13:09:48 UTC+1, fd_...@mail.com a écrit :
> Hi
>
>
>
> I want to check the linear independence of the columns on my matrix. I found the function DETERM() but this works only in cases where the matrix is NXN. In my case the matrix is NX4 (N-rows, 4-columns).
>
>
>
> How can I calculate the determinant of that matrix?
>
>
>
> Many Thanks
>
> Ma

> How can I calculate the determinant of that matrix?
You cannot, because determinant is not defined for a non square matrix.

> I want to check the linear independence of the columns on my matrix
What you are asking for is the rank of your matrix (i.e., mathematically, the number of independent columns). Matrix rank can be determined by singular value decomposition: the rank is the number of singular values which are not zero. In IDL, you can write:

if A is your matrix:
IDL> LA_SVD, A, W, U, V
IDL> rank_of_A = N_elements(W[where(W ne 0)])

alx.

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[Message index]

		Determinant of a matrix By: fd_luni on Wed, 20 November 2013 04:09
		Re: Determinant of a matrix By: Fabzi on Wed, 20 November 2013 04:44
		Re: Determinant of a matrix By: fd_luni on Wed, 20 November 2013 04:58
		Re: Determinant of a matrix By: lecacheux.alain on Wed, 20 November 2013 05:37
		Re: Determinant of a matrix By: fd_luni on Wed, 20 November 2013 06:57
		Re: Determinant of a matrix By: fd_luni on Wed, 20 November 2013 06:59
		Re: Determinant of a matrix By: Craig Markwardt on Wed, 20 November 2013 07:40
		Re: Determinant of a matrix By: fd_luni on Wed, 20 November 2013 07:53
		Re: Determinant of a matrix By: Craig Markwardt on Wed, 20 November 2013 08:33
		Re: Determinant of a matrix By: Mats Löfdahl on Wed, 20 November 2013 08:46
		Re: Determinant of a matrix By: Paul Van Delst[1] on Wed, 20 November 2013 09:04
		Re: Determinant of a matrix By: Craig Markwardt on Wed, 20 November 2013 18:33
		Re: Determinant of a matrix By: Paul Van Delst[1] on Thu, 21 November 2013 05:20

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