--- Prof Brian Ripley <[EMAIL PROTECTED]> wrote:
> On Thu, 4 May 2006, Guojun Zhu wrote: > > > I am still battling with my project :( > > > > I have a line like this > > > > > lm(month.model$next.ret~.,month.model,na.action=na.omit) > > Yourexamplesmightactuallybereeadableifyouusedyourspacebar. What do you mean here? > > next.ret ~ . would suffice here. > > > month.model is a data frame with lots of columns. > One > > of them is "Oth", a dummy variable. I checked > > month.model, there are two rows with number 1 and > > others are either 0 or NA. the two rows with > Oth==1 > > have no NA. I have totally about 900 rows. But > after > > the regression, the Oth's coefficient is NA. I do > not > > understand. > > You don't show us how you reach that conclusion, but > probably aliasing is > the cause. See ?alias. I edit my data frame. And check all the month.model. I see two 1 in that column, hundreds of 0 and a few NA. I have about 900 rows with 13 normal variables and 20 dummy variables. "Oth" is one of the dummy variables. I do not quite understand alias. The help is not clear. But I will try to read it again. > > > Another issue is also about NA. I offen use > something > > like "model[model$Oth==1,]", but it will not only > > gives rows with oth==1, but also gives some rows > with > > all item as NA. I then changed this into " > > > month.model[(month.model$Oth==1)&(!is.na(month.model$next.ret)),]" > > and it gives the same result. Finally I change it > > into > > " > > > month.model[(month.model$Oth==1)&(!is.na(month.model$Oth)),]" > > and it works. next.ret is a column for sure. Can > > anyone explain this to me? > > You want month.model$Oth %in% 1 > > Such things are covered with detailed examples in > chapter 2 of MASS4 (see > the FAQ). Is there any online materials available? I start R because it is free and would much rather to keep in that way. Thanks. > > > -- > Brian D. Ripley, > [EMAIL PROTECTED] > Professor of Applied Statistics, > http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 > 272861 (self) > 1 South Parks Road, +44 1865 > 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 > 272595 > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
