[R] spline interpolation

[Mike Marchywka]

> From: dwinsemius at comcast.net
> To: asanramzan at yahoo.com
> Date: Sat, 5 Feb 2011 10:24:04 -0500
> CC: r-help at r-project.org
> Subject: Re: [R] spline interpolation
>
>
> On Feb 5, 2011, at 9:29 AM, Asan Ramzan wrote:
>
> > Hello R-help
> > I have the following data for a standard curve
> > concentration(nM),fluorescence
> > 0,48.34
> > 2,58.69
> > 5,70.83
> > 10,94.73
> > 20,190.8
> > 50,436.0
> > 100, 957.9
> >
> > (1)Is there function in R to plot a spline.
>
> ?spline
>
> > (2)How can I interpolation,say 1000 point from 0nM-100nM and store
> > this as a
> > data frame of concentration,fluorescence
>
> ?approxfun

I was waiting for some other code to finish and thought I would give this a try.
I'm still learning R, maybe you can comment on this approach

# made data file 
f1<-read.table("d1.txt",sep=",")
ss<-smooth.spline(f1$V1,f1$V2)
# it is alwys good to look first.
plot(ss)
lines(ss)
str(ss)
ssi<-smooth.spline(f1$V2,f1$V1)
predict(ssi,200.3456)
predict(ssi,1:10)
predict(ssi,1:100)$y

etc



>
> > (3)How can I modify the code below so that instead of retrieving a
> > concentration
> > with the exact value of fluorescence, it gives me concentration for
> > the value
> > that is closest to that fluorescence.
>
> ?which.min #(although I would be using "[" rather than subset for
> that purpose.)
>
> >
> > subset(df,fluorescence==200.3456,select=concentration)
> >
> >

> David Winsemius, MD
> West Hartford, CT
>