Hi, Try this:
# using the iris dataset mydat <- iris mymodel <- lm(Sepal.Length ~ Petal.Length + Species, data = mydat) summary(mymodel) newdat <- data.frame(Petal.Length = seq(1, 10, by = .1), Species = factor(rep("virginica", 91))) results <- predict(object = mymodel, newdata = newdat, se.fit = TRUE) results The main lesson is that generally newdata should be a data frame with columns that have the same name as the predictors (IVs) in your model. I'm not exactly sure what you mean by "variance of dependent variable based on model". Do you want its total variance, residual variance, _______ ? Cheers, Josh On Mon, Sep 27, 2010 at 12:58 PM, Yi Du <abraham...@gmail.com> wrote: > Hi folks, > > I use lm to run regression and I don't know how to predict dependent > variable based on the model. > > I used predict.lm(model, newdata=80), but it gave me warnings. > > Also, how can I get the variance of dependent variable based on model. > Thanks. > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. > -- Joshua Wiley Ph.D. Student, Health Psychology University of California, Los Angeles http://www.joshuawiley.com/ ______________________________________________ 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.