[R] How to calculate the closest distance from a point to a curve?

Spencer Graves spencer.graves at pdf.com
Tue Feb 25 20:24:03 CET 2003

If you want the closest point to a fitted model, "predict" may work with 
the output of the fitting function to generate a column of y's;  see, 
e.g, Venables and Ripley, Modern Applied Statistics with S.  Then the 
nearest point can be found as Jose Lozano suggested.

Jose Lozano (MEGA) wrote:
>>Hely, R-list
>>Now I have non-parametric curve function, that is,
>>I only use N 2-Dimensional data points to represent
>>this curve, without explicit function formulation.
> (x,y) gives the points that define the curve (I've generated a circle 
> centered at 0)
> (a,b) is the point (I've set it to (2,2))
> x<-seq(from=-1,to=+1,length=1000)
> y<-sqrt(1-x^2)
> x<-c(x,x)
> y<-c(y,-y)
> n<-length(x)
> a<-2
> b<-2
> The code to find the closest point to (a,b) is:
> minimo<-min((1:n)[sqrt((a-x)^2+(b-y)^2)==min(sqrt((a-x)^2+(b-y)^2))])
> cat(x[minimo],y[minimo],"\n")
> 0.7077077 0.7065053 
> Regards
> Jose Lozano
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