comp.lang.idl-pvwave archive: archive » Re: SVDC - singular values not in decreasing order?

Home » Public Forums » archive » Re: SVDC - singular values not in decreasing order?

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: SVDC - singular values not in decreasing order? [message #82230]

Wed, 28 November 2012 14:11

Andy Sayer
Messages: 127
Registered: February 2009

Senior Member

Got it, thanks. :)

On Wednesday, November 28, 2012 1:58:51 PM UTC-5, AMS wrote:
> Hi all,
>
>
>
> I am interested in singular value decomposition in IDL, using the svdc routine.
>
>
>
> I had been under the impression that the singular values in such an analysis were given in descending order (order of importance of the singular vectors); see e.g. http://alias-i.com/lingpipe/demos/tutorial/svd/read-me.html So, the first vector explains the largest portion of variance, the second the next, and so forth.
>
>
>
> However, from my own analysis and also the example in the IDL help page (http://idlastro.gsfc.nasa.gov/idl_html_help/SVDC.html ), this is not the case (they are not in decreasing order). So, my questions are:
>
>
>
> 1. Is this intentional?
>
> 2. What does it mean? To find the 'n' most significant vectors, should I be taking the first 'n' returned by IDL, or the 'n' with the largest singular values?
>
>
>
> Any advice would be appreciated!
>
>
>
> Andrew

Report message to a moderator

[Message index]

		Re: SVDC - singular values not in decreasing order? By: Andy Sayer on Wed, 28 November 2012 14:11
		Re: SVDC - singular values not in decreasing order? By: Lajos Foldy on Wed, 28 November 2012 12:24
		Re: SVDC - singular values not in decreasing order? By: Andy Sayer on Wed, 28 November 2012 11:22
		Re: SVDC - singular values not in decreasing order? By: Lajos Foldy on Wed, 28 November 2012 11:12

Previous Topic:	SVDC - singular values not in decreasing order?
Next Topic:	Code to read bog standard DirectShow Windows webcam video?

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Wed Oct 08 15:36:22 PDT 2025

Total time taken to generate the page: 0.00376 seconds