On Mar 7, 2013, at 4:47 AM, Kjetil Kjernsmo <kje...@ifi.uio.no> wrote:
> On Wednesday 6. March 2013 16.33.34 Peter Claussen wrote: >> But you don't have enough data points to estimate all of the possible >> interactions; that's why you have NA in your original results. > > Yes, but it seems to me that lm is doing the right thing, or at least the > expected thing, here, the NA's are simply telling me these are aliased, which > is correct and expected. > I ran across the text you reference while looking up a couple other references yesterday; having read the appropriate section I can better understand your questions. I would say in this case that what R is doing is expected, but not necessarily correct, for this problem. The authors go into some detail about aliasing treatments, and that there are different choices for aliasing. I didn't have my computer handy, but does R choose the same set of aliases as the authors? Peter >> You could >> add the just the first order interactions manually, i.e., + B:C + B:D … > > Yeah, I tried that, but then it returns to the "unexpected" result, i.e., I > get the same result as with the yavg ~ B * C * D * E * Q formula. Therefore, > I > think the problem doesn't lie with the formula, nor does it lie with any of > the code, it is just a matter of understanding defaults... > > I have consulted local help (of course), but what they say is that "R has > some > odd defaults, you need to ask them or use something different". I don't want > to > use something different, I like R, I have contributed to R in the past and > will > do so again if only I can get my head around this... :-) > > Kjetil > > ______________________________________________ > 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. ______________________________________________ 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.
