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Re: How to Sort/Uniq a list and keep its original index [message #50698]

Thu, 12 October 2006 11:16

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Wed, 11 Oct 2006 17:12:07 -0600, David Fanning wrote:
>
> I haven't tested this, but just off the top of my head:
>
> I = Where(Histogram(indexU, Min=0, Max=N_Elements(testTotal)) $
> EQ 0, count)

I think that will leave out one of the duplicates of each set (since
one of them by definition is unique).

If you're going to use HISTOGRAM, you could use it to do the whole
thing:

h=histogram(testTotal,REVERSE_INDICES=ri)
wh=where(h gt 1,cnt) ;; bins with duplicates
for i=0,cnt-1 do do_something_with,ri[ri[wh[i]]:ri[wh[i]+1]-1]

since it's faster than SORT for well-behaved data. Notice that I didn't
explicitly test for empty bins, since I'm only looping over those bins
with 2 or more entries. If most of your duplicate counts are low (2x, 3x,
etc.), you can see another big speedup by binning the resulting histogram.
Standard sparse data warnings apply.

If you want to use SORT anyway (for simplicity, or for instance
because the data could be very sparse), your could just do the
opposite of what UNIQ does:

indexDUP=where((test eq shift(test,-1)) OR (test eq shift(test,1)))

JD

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[Message index]

		Re: How to Sort/Uniq a list and keep its original index By: JD Smith on Thu, 12 October 2006 11:16
		Re: How to Sort/Uniq a list and keep its original index By: Jean H. on Thu, 12 October 2006 09:19
		Re: How to Sort/Uniq a list and keep its original index By: David Fanning on Wed, 11 October 2006 16:12
		Re: How to Sort/Uniq a list and keep its original index By: Dilkushi@gmail.com on Wed, 18 October 2006 11:36

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