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Re: matrix division [message #60567 is a reply to message #60444]

Thu, 22 May 2008 08:48

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

jameskuyper@verizon.net writes:

> For the integer case:
>
> ratio = numerator/denominator
> bad = WHERE(denominator eq 0, count)
> IF count gt 0 THEN ratio[bad] = replacement_value
>
> replacement_value needs to be carefully chose for the context of your
> problem. You might want to give different replacement values depending
> upon whether the numerator is positive, negative, or 0. There's
> probably a more elegant approach, but three different WHERE's would
> certainly be sufficient to cover those cases.
>
> For the floating point case, IDL fills in the relevant elements of
> ratio with -Inf, Nan, or Inf, depending upon the sign of the
> numerator, and I can't think of any better way of handling it than to
> use precisely those value. If you need to use your result for further
> computations where those values would be unacceptable, replace them,
> with logic similar to the above, but using the FINITE() function.

Shoot. I was hoping for an elegant solution. :-(

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming (www.dfanning.com)
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		matrix division By: adam.ranson on Wed, 21 May 2008 11:29
		Re: matrix division By: Kenneth P. Bowman on Fri, 23 May 2008 13:41
		Re: matrix division By: David Fanning on Fri, 23 May 2008 12:18
		Re: matrix division By: Vince Hradil on Fri, 23 May 2008 11:02
		Re: matrix division By: Jean H. on Fri, 23 May 2008 10:23
		Re: matrix division By: Vince Hradil on Fri, 23 May 2008 10:06
		Re: matrix division By: Jean H. on Fri, 23 May 2008 09:41
		Re: matrix division By: edward.s.meinel@aero. on Fri, 23 May 2008 08:13
		Re: matrix division By: adam.ranson on Fri, 23 May 2008 01:47
		Re: matrix division By: Kenneth P. Bowman on Thu, 22 May 2008 13:15
		Re: matrix division By: Jean H. on Thu, 22 May 2008 12:28
		Re: matrix division By: David Fanning on Thu, 22 May 2008 10:45
		Re: matrix division By: Rich Younger on Thu, 22 May 2008 10:22
		Re: matrix division By: Rich Younger on Thu, 22 May 2008 10:13
		Re: matrix division By: edward.s.meinel@aero. on Thu, 22 May 2008 09:47
		Re: matrix division By: Paul Van Delst[1] on Thu, 22 May 2008 09:19
		Re: matrix division By: David Fanning on Thu, 22 May 2008 08:48

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