[R] read.dta function in foreign package

Thomas Lumley tlumley at u.washington.edu
Wed Jul 24 18:39:21 CEST 2002

On Wed, 24 Jul 2002, Ravi Varadhan wrote:

> Hi:
> When I import a Stata (version 7) data set into R, the missing values
> for factor and numeric variables are represented as "NaN", but the
> missing values for date variables are represented as "NA".  Can "NaN"
> for numeric variables be treated as the same as "NA" ? Are there
> situations when these two representations are not equivalent?

They are almost always treated the same way.  The few exceptions are
things like the function is.nan(), which is FALSE for NA, and the fact
that unique() on a vector containing NA and NaN will report them as
different values.

However, I'm surprised that you are getting NaNs. I get NA for missing
numeric data under both Windows and Linux (though the Windows version is
1.5.1), and the C source code looks as if it should give NA (I certainly
intended it to).


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