[SciPy-user] neighbourhood of randomly scattered points

[fred]

Robert Kern a écrit :
> White noise isn't all that uniform. It does clump, and some kinds of displays
> may show that off more than others. The orthogonal striations are a side effect
> of your square definition of "neighborhood" that you used to plot and not
> anything intrinsic to the data.
>
> If you do need something more spatially uniform than what real pseudorandomness
> gives you, then you should look at low-discrepancy sequences.
>
>   http://en.wikipedia.org/wiki/Low-discrepancy_sequence
>   
Sorry, I don't understand.

1) My algorithm to enumerate the number of neighbours in the 
neighbourhood does work fine
and has been validated.
2) http://fredantispam.free.fr/rect.png
shows the result for a rectangular neighbourhood. That's ok,
there are striations, but this is not the problem.
3) http://fredantispam.free.fr/circ.png
shows the result for a circular neighbourhood. There is no more striations.

The question is : why I get (for the circular case) around 90 neighbours
at il = xl = 450 and around 40 at il = xl = 200, ie less than half, if 
it is
completely random ?

I was expecting something more "uniform":
the mean is about 70 and the std about 10.

Cheers,

-- 
http://scipy.org/FredericPetit