Instead of using smooth.spline, use lm with spline terms, e.g.: > library(splines) > sp.fit <- lm(y~bs(x,4))
Now both use predict.lm for the predictions and all will be consistent. Hope this helps, -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-devel-boun...@r-project.org [mailto:r-devel-boun...@r- > project.org] On Behalf Of Christian Brechbühler > Sent: Monday, August 17, 2009 2:54 PM > To: r-de...@stat.math.ethz.ch > Subject: [Rd] Polymorphism of predict > > I can fit a line to a set of given points, e.g., > > > sm.fit <- smooth.spline(1:4,1:4) > > lm.fit <- lm(y~x, data=list(x=1:4,y=1:4)) > > Now I have two objects representing the straight line y(x)=x, of class > "smooth.spline" and "lm", respectively. > And as could be expected in object orientation, both have a method > "predict", which I could use for > interpolating some new points on the line. So far so good. BUT the > two > methods require different > arguments, and return different structures: > > > predict(sm.fit, 1.5:4) > $x > [1] 1.5 2.5 3.5 > > $y > [1] 1.5 2.5 3.5 > > > predict(lm.fit, list(x=1.5:4)) > 1 2 3 > 1.5 2.5 3.5 > > I probably don't understand the motivation behind this design, but it > seems > ugly. If, hoping for nice > polymorphism, I call predict(lm.fit, 1.5:4), I get an error: "numeric > 'envir' arg not of length one". > > I expected something like the classic OO example, class Shape: you can > call > area() or paint() on > any object of the class. > > Questions: > * Why does "predict" act so inconsistently? > * Is there a nicer interface that hides it? > * Are there plans to change the current design? > > Assuming "no" to the latter two -- what are my options? Create > as.smooth.spline(...) that would accept an "lm" object? > My goal is to write OO style code, that doesn't need to know which kind > it's > working with. > Thanks, > /Christian > > [[alternative HTML version deleted]] > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
