On Tue, Aug 26, 2008 at 6:45 PM, Ted Harding <[EMAIL PROTECTED]> wrote: > Hi Folks, > This tip is probably lurking somewhere already, but I've just > discovered it the hard way, so it is probably worth passing > on for the benefit of those who might otherwise hack their > way along the same path. > > Say (for example) you want to do a logistic regression of a > binary response Y on variables X1, X2, X3, X4: > > GLM <- glm(Y ~ X1 + X2 + X3 + X4) > > Say there are 1000 cases in the data. Because of missing values > (NAs) in the variables, the number of complete cases retained > for the regression is, say, 600. glm() does this automatically. > > QUESTION: Which cases are they? > > You can of course find out "by hand" on the lines of > > ix <- which( (!is.na(Y))&(!is.na(X1))&...&(!is.na(X4)) ) > > but one feels that GLM already knows -- so how to get it to talk? > > ANSWER: (e.g.) > > ix <- as.integer(names(GLM$fit))
Alternatively, you can use: attr(GLM$model, "na.action") Hadley -- http://had.co.nz/ ______________________________________________ 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.
