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Re: array chicanery [message #28052 is a reply to message #28051]

Thu, 15 November 2001 16:20

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Rochelle Hatton (nrh@imag.wsahs.nsw.gov.au) writes:

> I've experienced some wierd business with arrays, and I'm hoping somebody can explain.
> I have been using the IDL function PCOMP, calculating the pricipal components of some data.
> If I feed in a float array to the function,
> eg.
> result=PCOMP(data,coefficients=eigenvectors,eigenvalues=eige nvalues,/covariance,/standardize)
>
> I get a result, but when I redisplay the data array, it has changed. Since PCOMP only returns
> a result, what is it doing to my original array, and why? There are no common variables, as far
> as I know, so the original data should not change. I apologise in advance if this is blindingly
> obvious, and of course, I can just make a copy of the original data into another variable to use
> later, I am just curious as to what is going on.
> Any thoughts?

Lousy programming. On someone's part other than yours. :-)

Try this:

IDL> result=PCOMP(data+0,coefficients=eigenvectors,$
eigenvalues=eigenvalues,/covariance,/standardize)
IDL> Help, data

Does that help?

Cheers,

David
--
David W. Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155

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[Message index]

		Re: array chicanery By: David Fanning on Thu, 15 November 2001 18:33
		Re: array chicanery By: Mark Hadfield on Thu, 15 November 2001 17:49
		Re: array chicanery By: nrh on Thu, 15 November 2001 17:29
		Re: array chicanery By: Mark Hadfield on Thu, 15 November 2001 16:35
		Re: array chicanery By: nrh on Thu, 15 November 2001 16:28
		Re: array chicanery By: David Fanning on Thu, 15 November 2001 16:20

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