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Re: simple array math question [message #33809 is a reply to message #33713]

Fri, 24 January 2003 11:29

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

"Pepijn Kenter" <kenter@tpd.tno.nl> writes:
> "Kenneth Bowman" <k-bowman@null.tamu.edu> wrote in message
> news:k-bowman-4D0582.08381824012003@news.tamu.edu...
>> In article <b0rce6$23c$1@news.surfnet.nl>,
>> "Pepijn Kenter" <kenter@tpd.tno.nl> wrote:
>>
>>> And does any IDL-wizard know a similar trick to average each row/column
> of
>>> a?
>>> i.e. to replace the following lines:
>>>
>>> result = dblarr(3)
>>> for i = 0, 2 do result[i] = mean(a[*,i])
>>
>> That's an easy one:
>>
>> result1 = TOTAL(a, 1, /DOUBLE)/n1
>> result2 = TOTAL(a, 2, /DOUBLE)/n2
>>
>> where n1 and n2 are the sizes of the first and second dimensions,
>> respectively.
>>
>> Ken Bowman
>
> Thanks, but what I actually meant was a way where you can replace the mean
> function by any, arbitrary function.
> I forgot about the dimension parameter of the TOTAL function, so my example
> was a bad one. Sorry.

"Arbitrary function"? No. In more recent versions of IDL, quite a
number of built-in math functions have the ability to specify one or
more dimensions over which the function is to be applied. I have a
function called CMAPPLY, which may be useful with older versions of
IDL, and does many of those same things. One thing it can do is apply
an arbitrary function, but it won't necessarily be speedy. JD Smith
also has a DLM which did a lot of these kinds of things.

Good luck,
Craig

http://cow.physics.wisc.edu/~craigm/idl/idl.html (under Array/Set ops)

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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		simple array math question By: Sean Raffuse on Thu, 16 January 2003 12:05
		Re: simple array math question By: Pepijn Kenter on Tue, 28 January 2003 05:40
		Re: simple array math question By: Craig Markwardt on Mon, 27 January 2003 11:54
		Re: simple array math question By: JD Smith on Mon, 27 January 2003 10:20
		Re: simple array math question By: JD Smith on Mon, 27 January 2003 10:00
		Re: simple array math question By: Craig Markwardt on Sun, 26 January 2003 12:11
		Re: simple array math question By: Craig Markwardt on Fri, 24 January 2003 11:29
		Re: simple array math question By: Pepijn Kenter on Fri, 24 January 2003 07:50
		Re: simple array math question By: K. Bowman on Fri, 24 January 2003 06:38

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