[R] Counting observations split by a factor when there are NA s in the data
andy_liaw at merck.com
Mon Jul 10 21:30:45 CEST 2006
Wouldn't something like table(status) give you want you want? E.g.:
R> status <- factor(c("A", "B", "A", NA, "A", "B"))
From: Jenifer Larson-Hall
> I am a very novice R user, a social scientist (linguist) who
> is trying to learn to use R after being very familiar with
> SPSS. Please be kind!
> My concern:
> I cannot figure out a way to get an accurate count of
> observations of one column of data split by a factor when
> there are NAs in the data.
> I know how to use commands like tapply and summaryBy to
> obtain other summary statistics I am interested in, such as
> the following:
> tapply(RLWTEST, list(STATUS), mean, na.rm=T)
> summaryBy(RLWTEST~STATUS, data=lh.forgotten, FUN=c(mean, sd,
> min, max),
> However, with tapply I know I cannot use length to get a
> count where there are NAs. summaryBy appears to work the same
> way. I do know how to get a count of the entire column using sum:
> However, this does not give me a count split up by my factor
> (STATUS). I have looked through Daalgard (2002) and Verzani
> (2005), and have searched the help files, but with no luck.
> Thank you in advance for your help. I love R and am
> interested in making it more accessible to social scientist
> types like me. I know it can do everything SPSS can and more,
> but sometimes the very simplest things seem to be a lot harder in R.
> Dr. Jenifer Larson-Hall
> Assistant Professor of Linguistics
> University of North Texas
> R-help at stat.math.ethz.ch mailing list
> PLEASE do read the posting guide!
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