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Re: Matrix algebra and index order, A # B vs A ## B [message #79849 is a reply to message #79706]

Thu, 05 April 2012 07:55

Mats Löfdahl
Messages: 263
Registered: January 2012

Senior Member

I'm writing some code where matrix algebra is at the heart of things so I really wanted to understand the conventions and convince myself that I can use them in a consistent way.

I realized a major problem for me was not being able to inspect the matrices properly. The IDL print command can print arrays but because the arrays are interpreted as matrices differently depending on which convention is used, I was never sure of what I was looking at. So I wrote a subroutine that prints a matrix the way it is interpreted, based on the multiplication operator (which I think is a convenient way of specifying column-major/row-major). That really helped me make sense of it so I put it and some examples on a web page here: http://www.solarphysics.kva.se/~mats/idl/matrixalgebra/

I also satisfied myself that I understand the output of LA_SVD and QRfac and that they use the ## operator convention (with a little workaround for QRfac), see the same page.

OK, so this helped me understand what I'm doing. Does it address the frustration that you all have expressed in this thread or are there other issues that I just haven't realized yet?

/Mats

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[Message index]

		Matrix algebra and index order, A # B vs A ## B By: Mats Löfdahl on Mon, 26 March 2012 04:33
		Re: Matrix algebra and index order, A # B vs A ## B By: Mats Löfdahl on Wed, 28 March 2012 03:45
		Re: Matrix algebra and index order, A # B vs A ## B By: Mats Löfdahl on Thu, 05 April 2012 07:55
		Re: Matrix algebra and index order, A # B vs A ## B By: David Fanning on Tue, 27 March 2012 06:27
		Re: Matrix algebra and index order, A # B vs A ## B By: Craig Markwardt on Tue, 27 March 2012 06:11
		Re: Matrix algebra and index order, A # B vs A ## B By: Mats Löfdahl on Tue, 27 March 2012 00:45
		Re: Matrix algebra and index order, A # B vs A ## B By: Craig Markwardt on Mon, 26 March 2012 15:41
		Re: Matrix algebra and index order, A # B vs A ## B By: David Fanning on Mon, 26 March 2012 07:35
		Re: Matrix algebra and index order, A # B vs A ## B By: Mats Löfdahl on Thu, 05 April 2012 10:29
		Re: Matrix algebra and index order, A # B vs A ## B By: Kenneth P. Bowman on Thu, 05 April 2012 09:48
		Re: Matrix algebra and index order, A # B vs A ## B By: David Fanning on Thu, 05 April 2012 08:22

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