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Re: Histogram question [message #40475 is a reply to message #40375]

Tue, 10 August 2004 11:43

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Sun, 08 Aug 2004 18:52:57 +0000, Marshall Perrin wrote:

> Michael Wallace <mwallace.no.spam@no.spam.swri.edu.invalid> wrote:
>> I wrote this little snippet which doesn't use HIST_2D at all. It's just
>> a simple FOR loop and adding values. Back in the good ol' days, I would
>> have been satisfied with this, but after having read this newsgroup for
>> a while I just have a feeling that there's a way to get rid of that FOR
>> loop and do something totally cool with the HISTOGRAM function. So I
>> guess my question is more academic than anything else.
>
> It's too bad HIST_2D doesn't have a REVERSE_INDICES keyword like HISTOGRAM
> does. If it did, you could do something like
>
> H = hist_2d(v1,v2,reverse_indices=r)
> for i=0L,n_elements(h)-1 do
> H[i] += total(v3[R[R[I] : R[i+1]-1]] -1 )
>
>
> You could maybe still make this work if you don't mind unrolling your 2D
> arrays into 1D arrays somehow.

That's how HIST_2D does it's magic. The HIST_ND program I wrote also
gives you reverse indices (find it on David's site:
http://www.dfanning.com/programs/hist_nd.pro).

JD

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[Message index]

		histogram question By: Gregory Y. Prigozhin on Wed, 08 August 2001 13:17
		Re: histogram question By: Jim Pendleton on Thu, 09 August 2001 15:01
		Re: Histogram question By: Chris Lee on Mon, 09 August 2004 07:39
		Re: Histogram question By: mperrin+news on Sun, 08 August 2004 11:52
		Re: Histogram question By: JD Smith on Tue, 10 August 2004 11:43
		Re: Histogram question By: Michael Wallace on Sun, 08 August 2004 11:28
		Re: Histogram question By: David Fanning on Sun, 08 August 2004 06:40
		Re: Histogram question By: David Fanning on Tue, 10 August 2004 12:26

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