[R] Fw: length() misbehaving?: More

[David Parkhurst]

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.  Is this a bug, or is it to be expected?

Dave

Subject: length() misbehaving?


> 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
>
> the result is 68!  Any ideas why this is happening, and how I can fix the miscount?
> (That column also contains 69 entries of "c", and (relevantly?) two NA's.)
>
> Thanks for any help.
>
> Dave Parkhurst
>
>