Hi Rita, This is far from the most efficient or elegant way, but:
## two column data frame, one all NAs d <- data.frame(1:10, NA) ## use apply to create logical vector and subset d d[, apply(d, 2, function(x) !all(is.na(x)))] I am just apply()ing to each column (the 2) of d, the function !all(is.na(x)) which will return FALSE if all of x is missing and TRUE otherwise. The result is a logical vector the same length as the number of columns in d that is used to subset only the d columns with at least some non-missing values. For documentation see: ?apply ?is.na ?all ?"[" ?Logic HTH, Josh On Fri, Mar 18, 2011 at 3:35 PM, Rita Carreira <ritacarre...@hotmail.com> wrote: > > Dear List Members,I have 55 data frames, each of which with 272 variables and > 267 observations. Some of these variables are blanks but the blanks are not > the same for every data frame. I would like to write a procedure in which I > import a data frame, see which variables are blank, and delete those > variables. My data frames have variables named P1 to P136 and Q1 to Q136. > I have a couple of questions regarding this issue: > 1) Is a loop an efficient way to address this problem? If not, what are my > alternatives and how do I implement them?2) I have been playing with a single > data frame to try to figure out a way of having R go through the columns and > see which ones it should delete. I have figured out how to delete rows with > missing data (newdata <- na.omit(olddata)) but how do I do it for columns??? > Thank you very much for your help and have a great weekend! > Rita ________________________________________ "If you think education is > expensive, try ignorance"--Derek Bok > > > > [[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.
