Use generalised additive model to plot curve

Readers,

I have been reading 'the r book' by Crawley and think that the
generalised additive model is appropriate for this problem. The
package 'gam' was installed using the command (as root)

install.package("gam")
...
library(gam)

library(gam)

Loading required package: splines
Loading required package: akima

library(mgcv)

This is mgcv 1.3-25

Attaching package: 'mgcv'


        The following object(s) are masked from package:gam :

         gam,
         gam.control,
         gam.fit,
         plot.gam,
         predict.gam,
         s,
         summary.gam

x<-c(30,50,80,90,100)
y<-c(160,180,250,450,300)
model<-gam(y~s(x))

Error in smooth.construct.tp.smooth.spec(object, data, knots) :
        A term has fewer unique covariate combinations than specified
maximum degrees of freedom

The objective is to plot y against x, finally to produce a graph with
a smooth curve (and then remove the data points). What is my mistake
please?

yours,

r251
gnu/linux mandriva2008