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

Gael Varoquaux gael.varoquaux@normalesup....
Sat Feb 24 18:03:03 CST 2007


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
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.

The problem is that the "good" solution does depend on the problem, and
there will never be a one size fits all solution. I am interested in
other suggestions.

Cheers,

Gaël


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