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Number of points inside a contour curve [message #51947]

Wed, 20 December 2006 01:38

burkina
Messages: 32
Registered: February 2005

Member

What I need to do is basically simple, I guess, but I can't find an
easy way to do that.
I have an array of two parameters, let's call them x and y, each pair a
couple of measures taken simultaneously. I need to:

-Plot them in the x and y axis (at least this one is trivial!)

-Produce a density plot, i.e. divide the x-y space in discrete bins and
assign the number of points falling in each bin to that bin (This
should be done by hist_2D, but the results are fairly disappointing. A
better work is done by histogram_2d. Do you have any comments?)

-Plot confidence contour levels on that density plot, i.e. a contour at
the level where, say, 90% of points are contained. In other words, you
can use the normal contour IDL procedure, but you must find a way to
count all points lying inside this contour, in order to set the level
for the contour plot. The procedure should be able to find the
iso-count curve which encompass 90% of the total points.

So... I'm not sure I'm doing the right/best thing for point 2
(hist_2d/histogram_2d) and have no idea how to do point 3. However,
this problem seems to me quite common, because it's a way to find
statistical confidence level for a distribution of two parameters.

Can you help me?

Thanks,

Stefano

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[Message index]

		Number of points inside a contour curve By: burkina on Wed, 20 December 2006 01:38
		Re: Number of points inside a contour curve By: burkina on Fri, 22 December 2006 02:24
		Re: Number of points inside a contour curve By: David Fanning on Thu, 21 December 2006 07:55

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