search for: byyr

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 <- lengt...

With the problem below, I've discoved that n95trt<-length(byyr$cnd95[byyr$cnd95=="tr"&!is.na(byyr$cnd95)]) does give me the correct count for the number of "tr" entries. (The same behavior occurs for the "c" level of the cnd95 factor.) It appears that byyr$cnd95=="tr" is finding both "tr" AND NA entries....