On Tue, 14 Apr 2009, jimm-pa...@gmx.de wrote:
Hi all,
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, yes, but as Burt suggests it may not be sensible.
There are several ways. For one, include a reflection of the
(x,y) data into opposite quandrants as well as the original data.
Something like
l1<-loess( y ~ x , span=0.1, data.frame(x = c(-x1,x1), y = c(-y1,y1)),
control=loess.control(surface="direct"))
will force the prediction through the origin.
(I corrected what seems to be as typo in your code, too.)
Of course, if any( x < 0 ) it is hard to see how the substantive results
would make any sense.
HTH,
Chuck
Thanks in advance.
Cheers,
Torsten
--
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
