Hello, I have a couple of questions about the ols function in Frank Harrell's rms package.
Is there any way to specify variables by their column number in the data frame rather than by the variable name? For example, library(rms) x1 <- rnorm(100, 0, 1) x2 <- rnorm(100, 0, 1) x3 <- rnorm(100, 0, 1) y <- x2 + x3 + rnorm(100, 0, 5) d <- data.frame(x1, x2, x3, y) rm(x1, x2, x3, y) lm(y ~ d[,2] + d[,3], data = d) # This works ols(y ~ d[,2] + d[,3], data = d) # Gives error Error in if (!length(fname) || !any(fname == zname)) { : missing value where TRUE/FALSE needed However, this works: ols(y ~ x2 + d[,3], data = d) The reason I want to do this is to program variable selection for bootstrap model validation. A related question: does ols allow "y ~ ." notation? lm(y ~ ., data = d[, 2:4]) # This works ols(y ~ ., data = d[, 2:4]) # Gives error Error in terms.formula(formula) : '.' in formula and no 'data' argument Thanks for any help you can give. Regards, Mark -- Mark Seeto Statistician National Acoustic Laboratories <http://www.nal.gov.au/> A Division of Australian Hearing 126 Greville Street Chatswood NSW 2067 Australia P +61 2 9412 6800 F +61 2 9411 8273 ______________________________________________ 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.