[R] length() misbehaving?
tlumley at u.washington.edu
Fri Mar 14 18:35:35 CET 2003
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"])
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.
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