[R] confidence interval

[David Winsemius]

On Jan 21, 2011, at 11:33 AM, Francesco Petrogalli wrote:

> Hi,
> I have a circular shaped set of point on the plane (X,Y) centered in
> zero. The distribution is more dense close to zero and less dense far
> from zero.
>
> I need to find the radius of a circle centered in zero that contains
> 65% of the points in the sample. Is there any R directive that can do
> this?
>
> I wanna start with 2D set of points, but the real case scenario is
> with a 5D set of points.

Something along the lines of

dxy= with(dfm, sqrt(x^2 +y^2))
quantile(dxy, probs=0.65)

The generalization to 5 dimensions appears trivial. Even the  
generalization to finding the radius around an arbitrary point seems  
trivial assuming an L2 norm.

-- 
David Winsemius, MD
West Hartford, CT