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Re: matrix division [message #60569 is a reply to message #60422]

Thu, 22 May 2008 07:57

jameskuyper
Messages: 79
Registered: October 2007

Member

David Fanning wrote:
> James Kuyper writes:
>
>> What if b is < 0?
>
> I was hoping you would tell me, so I didn't have to
> think about it anymore. :-(

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.

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[Message index]

		Re: matrix division By: David Fanning on Thu, 22 May 2008 05:59
		Re: matrix division By: David Fanning on Thu, 22 May 2008 05:55
		Re: matrix division By: jameskuyper on Thu, 22 May 2008 05:47
		Re: matrix division By: jameskuyper on Thu, 22 May 2008 05:42
		Re: matrix division By: d.poreh on Thu, 22 May 2008 05:40
		Re: matrix division By: David Fanning on Thu, 22 May 2008 05:29
		Re: matrix division By: d.poreh on Thu, 22 May 2008 05:24
		Re: matrix division By: David Fanning on Thu, 22 May 2008 05:13
		Re: matrix division By: David Fanning on Thu, 22 May 2008 05:08
		Re: matrix division By: adam.ranson on Thu, 22 May 2008 04:41
		Re: matrix division By: d.poreh on Thu, 22 May 2008 03:07
		Re: matrix division By: Nigel Wade on Thu, 22 May 2008 03:00
		Re: matrix division By: adam.ranson on Thu, 22 May 2008 01:07
		Re: matrix division By: David Fanning on Wed, 21 May 2008 11:35
		Re: matrix division By: jameskuyper on Thu, 22 May 2008 07:57

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