Donald Lehmann <[EMAIL PROTECTED]> writes: > Dear Consultant > > I've done linear regression successfully on R a few times before. But > this time it keeps telling me:- > > "Error in lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) : > 0 (non-NA) cases" > > The model is:- > > fm1 <- lm(TS.CM ~ AGE + SEX + HFE.Y.01 + TFC2B.01 + HFE.Y.01*TFC2B.01, > data = IRONresults, subset = DIAG2.1D == 0) > summary (fm1) > > TS.CM is a continuous variable (%s), sex is coded 0 = women, 1 = men, > DIAG2.1D is coded 0 = non-demented, 1 = ALzheimer's disease and the > genes, HFE.Y.01 & TFC2B.01, are coded 0 = non-carrier and 1 = carrier > > I've tried recoding the data to use 1 & 2, instead of 0 & 1, and I've > removed the rows with missing data. I've also tried putting > "...lm(formula = TS.CM ~ ..." But I always get the same error message > > What am I doing wrong?
You don't need to give the main effects when there's a "*" term (that's a SASism, the R equivalent is ":" and a*b == a+b+a:b by definition), but that is hardly the main problem. Could you have a look at this? : with(IRONresults, complete.cases(TS.CM, AGE, SEX, HFE.Y.01, TFC2B.01)) If you get all FALSE, you'll know what hit you... > A related question: what's the minimum no of data points for > regression analysis to work? We have only 23 cases carrying both > genes out of 447 and only 8 out of 264 in the above subset (ie > non-demented). I seem to remember hearing somewhere that you needed a > minimum of ~30 (?), so probably this wouldn't work anyway. Still, I'd > like to know what I was doing wrong! Technically, you just need linearly independent predictors and more observations than parameters (incl. the intercept). Other bounds get bandied about on what should be required for a *meaningful* analysis (like "10 observations per parameter"), but these are quite heuristic and empirical in nature. -- O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
