I have noticed a slightly puzzling behaviour exhibited by
smooth.spline(). If I do
sss <- smooth.spline(x,y)
for a certain pair of data vectors x and y, and then do
length(sss$x)
I get the result ``18''. However if I do
length(unique(x))
I get ``27''. Trying to force smooth.spline() to use more knots I
tried
sss <- smooth.spline(x,y,all.knots=TRUE)
but again got output of length 18 again. I then tried
sss <- smooth.spline(x,y,nknots=27)
and got an error message. Finally I was inspired to re-scale the
x-values. Doing
x <- x - min(x)
sss <- smooth.spline(x,y)
gave me output of length 27 as expected. Apparently smooth.spline()
is using a criterion for distinctness of x values which is based on a
tolerance relative to the size of the x's. (I.e. a different
criterion from unique().) While this is assuredly a Good Thing, it
might be nice to have some sort of warning in the help file to keep
young players from getting confused.
cheers,
Rolf Turner
[EMAIL PROTECTED]
______________________________________________
[email protected] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
