On Wed, Aug 19, 2009 at 3:52 PM, Greg Snow <greg.s...@imail.org> wrote:
> 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 Hi Greg, This is opposite to the way I was thinking, because the rest of our code assumes splines. But your solution is clean and elegant. Thank you /Christian > > -----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 > [[alternative HTML version deleted]]
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