Return relative distance between two representative tree rings
rdst(L, P, yr)
list of x,y coordinates of representative tree rings (TR@L)
data.frame (x,y,id,yr,r,deg) of radial tree ring points (TR@P)
year
a data frame with relative distance and center angle
rdst.<-rdst(TR@L,TR@P,73)
plot(rdst.)
spline<-smooth.spline(rdst.$rad,rdst.$rdst, spar =0.0002)
lines(predict(spline,seq(-pi,pi,0.01)),col="red")