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Re: Iso-contours at maximum/minimum levels [message #64881 is a reply to message #64880]

Thu, 29 January 2009 14:51

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Gianluca Li Causi writes:

> In order to find the iso-value lines of a 2D surface I'm using the
> CONTOUR procedure, which works very well except that it's NOT ABLE to
> compute the contour when the LEVEL equals the maximum or minimum of
> the function.
>
> I've the following simple fuction:
> Z = shift(dist(100, 100), 50,50)
> Z = abs(Z - max(Z)*.3)
> which have a circular minimum at LEVEL=0, but CONTOUR is unable to
> find it!

According to my colleague Matt, what you should see at the
minimum of a contour plot is....nothing! I think I have to
agree. A contour line is suppose to enclose something.
What could be enclosed at the minimum value of a data set?
Right. Nothing.

You could hold a flat sheet of paper under your 2D surface
and draw a line where the surface touched the paper. But
the word for that would be an "etching" or an "imprint",
not a "contour". What you want, and what a contour plot
is designed to give, are two different things. Or at least
it seems that way to us. :-)

Cheers,

David

--
David Fanning, Ph.D.
Coyote's Guide to IDL Programming (www.dfanning.com)
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: Iso-contours at maximum/minimum levels By: pgrigis on Fri, 30 January 2009 11:00
		Re: Iso-contours at maximum/minimum levels By: David Fanning on Fri, 30 January 2009 07:48
		Re: Iso-contours at maximum/minimum levels By: pgrigis on Fri, 30 January 2009 07:36
		Re: Iso-contours at maximum/minimum levels By: David Fanning on Fri, 30 January 2009 07:21
		Re: Iso-contours at maximum/minimum levels By: Jeremy Bailin on Fri, 30 January 2009 07:04
		Re: Iso-contours at maximum/minimum levels By: pgrigis on Thu, 29 January 2009 15:14
		Re: Iso-contours at maximum/minimum levels By: David Fanning on Thu, 29 January 2009 14:51
		Re: Iso-contours at maximum/minimum levels By: David Fanning on Thu, 29 January 2009 08:15
		Re: Iso-contours at maximum/minimum levels By: Gianluca Li Causi on Mon, 02 February 2009 04:14

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