On Tue, Apr 14, 2009 at 1:08 PM, <jimm-pa...@gmx.de> wrote:
> I'm fitting a line to my dataset. Later I want to predict missing values that
> exceed the [min,max] interval of my empirical data, therefore I choose
> surface="direct" for extrapolation.
>
> l1<-loess(y1~x1,span=0.1,data.frame(x=x1,y=y1),control=loess.control(surface="direct"))
>
> In my application it is highly important that the fitted line intercepts at
> the point of origin. Is it possible to do this in R?
Well, you could always add lots of artificial data points x=0, y=0
..., like this:
l1<-loess(y1~x1,span=0.1,data.frame(x=c(rep(0,100),x1),y=c(rep(0,100),y1)),control=loess.control(surface="direct"))
which will eventually drive f(0) to near 0, but surely that will
create fitting artifacts.
-s
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