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Re: Using histogram (or cghistogram) to get top X percent of distribution? [message #92623 is a reply to message #92620]

Tue, 26 January 2016 06:37

Helder Marchetto
Messages: 520
Registered: November 2011

Senior Member

On Monday, January 25, 2016 at 9:48:23 PM UTC, rj...@le.ac.uk wrote:
> I'm not sure if this is just me not quite understanding how histogram works.
>
> I have a large array containing data. I want to identify the array indices of the top 10% (for example) of the data. I thought I should be able to use histogram to do this quickly but can't figure out how.
>
> Any help much appreciated as always :-)

Hi,
I normally do something very similar to scale images: I clip the histogram around a few percent from the lowest and highest side. This can be a good reference to find those pixels...
Here is the histogram to perform the histogram percentage clipping: http://idl.marchetto.de/percentage-of-histogram/

It's not very clean, but works fine for me.

Cheers,
Helder

PS: previously I searched the cumulative histogram until I hit the percentage I wanted, but using value_locate is more efficient.

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[Message index]

		Using histogram (or cghistogram) to get top X percent of distribution? By: rjp23 on Mon, 25 January 2016 13:48
		Re: Using histogram (or cghistogram) to get top X percent of distribution? By: Helder Marchetto on Tue, 26 January 2016 06:37
		Re: Using histogram (or cghistogram) to get top X percent of distribution? By: Med Bennett on Tue, 26 January 2016 07:38
		Re: Using histogram (or cghistogram) to get top X percent of distribution? By: Med Bennett on Tue, 26 January 2016 07:46
		Re: Using histogram (or cghistogram) to get top X percent of distribution? By: penteado on Wed, 27 January 2016 06:26
		Re: Using histogram (or cghistogram) to get top X percent of distribution? By: pfp on Wed, 27 January 2016 06:51

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