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Re: Number of points within a rectangular region [message #36845 is a reply to message #36840]

Fri, 31 October 2003 10:50

btt
Messages: 345
Registered: December 2000

Senior Member

Isa Usman wrote:
> Hello,
>
> I'm trying to get the indices to the points that fall within a rectangular
> region. I'm aware of David Fanning's INSIDE routine that does this but
> because I have got 100,000 points its going to involve a lot of looping. So
> I decided to use the HIST_ND with reverse indices but its not giving me the
> right results. What am I missing?
>
> Thanks in advance.
>
> Isa
>
> IDL> x = [0.5,-0.5,-0.5,0.5]
>
> IDL> y = [0.5,0.5,-0.5,-0.5]
>
> IDL> z = transpose([[x],[y]])
>
> IDL> result = hist_nd(z,min = [0,0], max = [1,1], nbins = 1, reverse_indices
> = ri)
>
> print, ri[ri[0]:ri[1]-1]
>
> 0 1 2 3
>
>

Hi,

You're mostly OK - but HISTOGRAM, and therefore HIST_ND, is sensitive to data
typing issues. Make sure that MIN, MAX and (if you were to use it) BINSIZE are
the same type as the input data.

Ben

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		Re: Number of points within a rectangular region By: Paul Sorenson on Sat, 01 November 2003 11:13
		Re: Number of points within a rectangular region By: wmconnolley on Sat, 01 November 2003 06:58
		Re: Number of points within a rectangular region By: btt on Fri, 31 October 2003 10:50

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