Well, (have you read "An Intro to R," which I think might have enabled you to figure this out for yourself?)....
Convert the factor to character, use is.na() to substitute, convert back to factor. e.g. > z <- factor (c(1,2,3,NA)) > z<- as.character(z) > z[is.na(z)] <- "U" > factor(z) [1] 1 2 3 U Levels: 1 2 3 U HOWEVER, this is almost certainly a BAD IDEA, as you have now essentially lost the ordering of the levels, which is important information for modeling. In general, R handles NA's (perhaps not always gracefully) and you should leave them as such and let R do its job. A lot of effort by wise folks has been expended to make this possible. Cheers, Bert On Tue, Jan 18, 2011 at 2:25 PM, <kurt_h...@nps.gov> wrote: > Greetings > I have a bunch of NAs in a column of categorical variables designating > the size classes (e.g., smallest to largest: 1,2,3,4) of cave crickets. > I'd like to substitute "U" (for unknown) for the NAs. Can anyone give me > an idea how to do this? Thanks in advance. > Cheers > Kurt > > *************************************************************** > Kurt Lewis Helf, Ph.D. > Ecologist > EEO Counselor > National Park Service > Cumberland Piedmont Network > P.O. Box 8 > Mammoth Cave, KY 42259 > Ph: 270-758-2163 > Lab: 270-758-2151 > Fax: 270-758-2609 > **************************************************************** > Science, in constantly seeking real explanations, reveals the true majesty > of our world in all its complexity. > -Richard Dawkins > > The scientific tradition is distinguished from the pre-scientific tradition > in having two layers. Like the latter it passes on its theories but it > also passes on a critical attitude towards them. The theories are passed > on not as dogmas but rather with the challenge to discuss them and improve > upon them. > -Karl Popper > > ...consider yourself a guest in the home of other creatures as significant > as yourself. > -Wayside at Wilderness Threshold in McKittrick Canyon, Guadalupe Mountains > National Park, TX > > Cumberland Piedmont Network (CUPN) Homepage: > http://tiny.cc/e7cdx > > CUPN Forest Pest Monitoring Website: > http://bit.ly/9rhUZQ > > CUPN Cave Cricket Monitoring Website: > http://tiny.cc/ntcql > > CUPN Cave Aquatic Biota Monitoring Website: > http://tiny.cc/n2z1o > > ______________________________________________ > 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. > -- Bert Gunter Genentech Nonclinical Biostatistics ______________________________________________ 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.
