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

[Spencer Graves]

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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