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Re: histogram & reverse_indices [message #30220 is a reply to message #30071]

Tue, 09 April 2002 13:47

Wayne Landsman
Messages: 117
Registered: January 1997

Senior Member

Ken Mankoff wrote:

>
> I have a 2D array made up of n quadruplets. Ex:
> array =[[1,1,1,2], $
> [1,1,1,1], $
> [3,4,3,2], $
> [3,3,0,0], $
> [5,5,0,5]]
>
> I want my algorithm to do the following: Return the index of all the
> quadruplets that have at least 3 out of 4 numbers equal to each other
> (i.e. for the above array, it should return [0,1,4]

Here's a non-loop solution for the specific case, although it is a
solution that is difficult to generalize, and which may be less
understandable and slower than simply using a loop.

The idea is that if 3 out of 4 numbers are equal to each other, then that
number is either the minimum or the maximum of the quadruplet. So we
first get the min and max of each quadruplet.

amin = min(array,dimen=1,max=amax) ;V5.5 needed

Now reform/rebin the min and max vectors into a 2d arrays

amax = rebin(reform(amax,1,5),4,5)
amin = rebin(reform(amin,1,5),4,5)

Now find which values in the array are equal to either the minimum or the
maximum. Total along rows
to determine if 3 or more values in a quadruplet meet this condition:

print,where( (total((array EQ amin),1) GE 3) or $
(total((array EQ amax),1) GE 3))

---> [0,1,4]

--Wayne
landsman@mpb.gsfc.nasa.gov

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[Message index]

		histogram & reverse_indices By: Ken Mankoff on Tue, 09 April 2002 12:15
		Re: histogram & reverse_indices By: Ken Mankoff on Wed, 10 April 2002 07:26
		Re: histogram & reverse_indices By: the_cacc on Wed, 10 April 2002 03:02
		Re: histogram & reverse_indices By: Craig Markwardt on Tue, 09 April 2002 19:35
		Re: histogram & reverse_indices By: Wayne Landsman on Tue, 09 April 2002 13:47

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