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Re: Finding the median of a set of images [message #6138 is a reply to message #6136]

Fri, 19 April 1996 00:00

Joseph M Zawodny
Messages: 24
Registered: March 1996

Junior Member

David Foster wrote:
>
> Dyer Lytle <dlytle@as.arizona.edu> wrote:
>>
>> Hello all,
>>
>> Does anyone have an algorithm for finding the median at each pixel
>> position for a set of equal size 2-D images? Currently the only way
>> I have to do this is to extract all the values for a given pixel
>> position into a 1-D array and find the median on that.
>
> This sounds like a good candidate for using CALL_EXTERNAL to
> call a routine coded in C or Fortran! If someone can think
> of an array-based way to do this in IDL I would be very
> impressed.
>
> If you are unfamiliar with using CALL_EXTERNAL zap me an
> email and I'll send you some sample code using C routines.
> The manual also has some examples, in the Advanced Development
> Guide (RSI will send you one [free!] by request only).
>
> Sorry this isn't what you wanted to hear.

I think that this should be native to IDL and not require a
CALL_EXTERNAL call. I also think that MEDIAN should be modified to add
this functionality in exactly the same way TOTAL was modified to sum over
requested dimensions of a multi dimensional array. My particular need
is to compute the median profile (one dimesional rather than two) of a
set of profiles. RSI has already solved the basic problem when they
enhanced TOTAL and so it should be relatively straight forward to add
this to MEDIAN (and MEAN and STDDEV and ...).

Just $0.02
--
Work: Dr. Joseph M. Zawodny Play: Joe Zawodny
NASA Langley Research Center KO4LW@amsat.org
E-mail: J.M.Zawodny@LaRC.NASA.gov zawodny@exis.net

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[Message index]

		Re: Finding the median of a set of images By: Dyer Lytle on Wed, 24 April 1996 00:00
		Re: Finding the median of a set of images By: peter on Fri, 19 April 1996 00:00
		Re: Finding the median of a set of images By: Joseph M Zawodny on Fri, 19 April 1996 00:00
		Re: Finding the median of a set of images By: steinhh on Fri, 19 April 1996 00:00
		Re: Finding the median of a set of images By: David Foster on Thu, 18 April 1996 00:00

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