From: David Soloveichik <dsolov_at_caltech.edu>

Date: Sun 28 May 2006 - 16:19:02 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun May 28 16:23:47 2006

Date: Sun 28 May 2006 - 16:19:02 EST

I am wondering whether there is a well-accepted approach to handling
missing values (NA's) in a programming language such as R. For
example, most functions seem to propagate NA to the output when the
value of the missing entry could have mattered. In other words, most
functions are not willing to "take a stand" on what the missing value
was. However, some functions don't seem to do this. For example,

> c(1,2,3,NA) %in% c(2,3)

**[1] FALSE TRUE TRUE FALSE
**
rather than: FALSE TRUE TRUE NA

Also, what is the logic of the following:

> c(1,2,3,NA) %in% c(2,3,NA)

**[1] FALSE TRUE TRUE TRUE
**
Why is the last output value TRUE? Why does R claim that the NA on
the left hand side of %in% is the same as the NA on the right hand
side of %in%?

Thanks a lot,

David

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun May 28 16:23:47 2006

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