Dr. Harrell, Thanks for your patient replies. I've two more questions:
1) Is your book appropriate for beginners or is it more for advanced users? 2) f <- ols(y ~ rcs(x,3), data=mydata) Function(f) does not produce anything for me (i.e.) it's empty. Sincerely, sp --- On Tue, 12/23/08, Frank E Harrell Jr <f.harr...@vanderbilt.edu> wrote: > From: Frank E Harrell Jr <f.harr...@vanderbilt.edu> > Subject: Re: [R] newbie problem using Design.rcs > To: to_rent_2...@yahoo.com > Cc: "David Winsemius" <dwinsem...@comcast.net>, r-help@r-project.org > Date: Tuesday, December 23, 2008, 4:57 PM > sp wrote: > > 2. I didn't have x^3 b/c that co-efficient happens > to be zero in this fitting. > > That's strange. > > > > > Also, I'm forced to call win.graph() before my > first plot() to see the first plot. Is that normal? > > no > > > > > I started with testing it on just x,y dimensions so > that I can visually evaluate the fitting. I tried y=x, y=x^2 > etc, adding Gaussian noise each time (to the y). > > I plot original x,y and x,y' where y' is > calculated using the co-efficients returned by rcs. I find > that the regression curve differs from the actual points by > as high as 10^5 with 3 knots and roughly -10^5 with 4 knots > as I make y=x^2, y=x^3.... > > wait until you have studied regression > > Frank > > > > > > If this is NOT a good way to test fitting, could you > pls tell me a better way? > > > > Respectfully, > > sp ______________________________________________ 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.
