[S] Re: spline (was: no subject)

Z. Todd Taylor (Todd.Taylor@pnl.gov)
Thu, 05 Mar 1998 09:35:20 -0800


Jan Schelling <schelling@ivuk.mavt.ethz.ch> wrote:

> Assuming your data is really
>
> x<-c(-3.9,-2,-0.22,0.1,4,7,9) # x and y must have the same length
> y<-c(-15,-7,-1,-0.22,2,8,13)
>
> you could use:
>
> sp <- spline(x,y, n=100) # interpolating spline with a 'large' number of pairs
> approx(sp$y, sp$x, 0)$y # reverse linear interpolation

What will approx do when there is not a functional relationship
in the reversed spline (x ~ y)? This is not the case in your
modification of the original data, but is very likely in
general.

--Todd

-- 
Z. Todd Taylor
Pacific Northwest National Laboratory
Todd.Taylor@pnl.gov
Why isn't it "heels over head"?
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