On May 3, 2013, at 17:24 , jpm miao wrote: > I have a program, when I write > > if(num!=NA) > > it yields an error message. > > However, if I write > > if(is.na(num)==FALSE) > > it works. > > Why doesn't the first statement work?
Because comparison with an unknown value yields an unknown result. By the way, comparing a logical value to FALSE is silly: if ( !is.na(num) ) will do it. -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.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.
