On Fri, 14 Mar 2003, David Parkhurst wrote: > I'm having a weird problem with length(), in R1.6.1 under windows2000. I have a > dataframe called byyr, with ten columns, the first of which is named cnd95. > summary(byyr) shows that byyr$cnd95 contains the factor level "tr" 66 times. Also, > when I enter byyr$cnd95 at the command line, I can count 66 "tr" elements in the > resulting vector. However, when I enter > > n95trt <- length(byyr$cnd95[byyr$cnd95=="tr"]) > n95trt >
In addition to the sum() approach suggested by other people there's an approach using %in% n95trt <- length(byyr$cnd95[byyr$cnd95 %in% "tr"]) You can check that NA=="tr" returns NA, but NA %in% "tr" returns FALSE. -thomas ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help