[SciPy-user] Carateristic distance in a cloud of points

Gael Varoquaux gael.varoquaux@normalesup....
Sat Feb 24 18:10:39 CST 2007


Correcting a stupid mistake. It bothered me to leave it, sorry for the
noise.

Gaël

On Sun, Feb 25, 2007 at 01:03:03AM +0100, Gael Varoquaux wrote:
> Interesting remarks. You forced me to think a bit more about what I was
> trying to achieve.

> What I am trying to do is to find out the right size to use for symbols
> when used on a 3D cloud of points. I am not sure what the right "typical
> distance" should be used. If those symbols are arrows then it seems that
> should be smaller than the typical inter-point distance. I have in mind
> something like this:

> if you have n points, find out the distribution of distances, divide it
> by n**3, then take the value at 0.2 from the smallest. 

> I am having diffculties expressing my point, but the idea would be to
> consider that the typical distribution will increase as n**3 (which is
							n**(1/3.)
> not obvious, for instance if the points are along a plane) and take the
> lower tail of the distribution, as we are interested in having symbols
> smaller than the inter-point distance. Taking not the smallest value, but
> the value at "20%" from the bottom helps getting rid of singular
> situations where a few points are very close but the major part is spread
> out.




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