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Re: zonal means [message #11342 is a reply to message #11082]

Mon, 23 March 1998 00:00

James Tappin
Messages: 54
Registered: December 1995

Member

Evilio del Rio wrote:
>
> Martin Schultz wrote:
>> ...
>> Q: How do you compute zonal means from a 3D data cube ?
>> (example: A(72,46,14) is a data array with longitude, latitude, altitude
>> as dimensions, and I want to compute the averages over longitude for
>> each latitude and altitude)

> In my opinion you should use the TOTAL function with a second argument:
>
> IDL> help,a
> A FLOAT = Array[72, 46, 14]
> IDL> b = TOTAL(A,1) ; The argument 1 tells TOTAL to sum just in the
> first dim.

Now for the $64,000 question -- how do you do the same thing for
medians? What we need here is an index argument to SORT analogous to the
second argument of TOTAL. Methinks that the only efficient solution is
currently to write the confounded thing as a CALL_EXTERNAL piece of C
code.

--
+------------------------+-------------------------------+-- -------+
| James Tappin, | School of Physics & Astronomy | O__ |
| sjt@star.sr.bham.ac.uk | University of Birmingham | -- \/` |
| Ph: 0121-414-6462. Fax: 0121-414-3722 | |
+--------------------------------------------------------+-- -------+

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[Message index]

		zonal means By: Martin Schultz on Mon, 16 March 1998 00:00
		Re: zonal means By: Craig Markwardt on Wed, 18 March 1998 00:00
		Re: zonal means By: Karsten Rodenacker on Wed, 18 March 1998 00:00
		Re: zonal means By: Karsten Rodenacker on Wed, 18 March 1998 00:00
		Re: zonal means By: Karsten Rodenacker on Wed, 18 March 1998 00:00
		Re: zonal means By: Karsten Rodenacker on Wed, 18 March 1998 00:00
		Re: zonal means By: Martin Schultz on Tue, 17 March 1998 00:00
		Re: zonal means By: Martin Schultz on Mon, 23 March 1998 00:00
		Re: zonal means By: James Tappin on Mon, 23 March 1998 00:00

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