[R] Excluding levels in table and xtabs

[Thomas Lumley]

On Wed, 11 Dec 2002, Michael Friendly wrote:

> I'm trying to form contingincy tables among a set of character variables
> which were read from a .csv file and
> have missing represented as "".  I want to exclude the missing levels
> from the table.

I think this is a bug. The exclude= argument doesn't work for factors,
because the argument is passed to factor(), and its exclude argument has
a different format when the main argument is a factor.

	-thomas


>
> > levels(CPIC)
> [1] ""  "N" "Y"
> > levels(Manix)
> [1] ""  "N" "Y"
> > xtabs(~CPIC + Manix, exclude=c("",NA))
>     Manix
> CPIC        N    Y
>      272    4   15
>    N 154 2812 1472
>    Y 158  466 4870
>
> > table(CPIC, Manix, exclude=c("",NA))
>
>     Manix
> CPIC        N    Y
>      272    4   15
>    N 154 2812 1472
>    Y 158  466 4870
>
> The only way I can exclude them is by
>
> t <- table(CPIC, Manix)
> t <- t[-1,-1]
>
> that's not to hard in this case, but my application is to a much
> larger table where this gets unweildly.
>
> --
> Michael Friendly              friendly at yorku.ca
> York University               http://www.math.yorku.ca/SCS/friendly.html
> Psychology Department
> 4700 Keele Street             Tel:  (416) 736-5115 x66249
> Toronto, Ontario, M3J 1P3     Fax:  (416) 736-5814
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help
>

Thomas Lumley			Asst. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle
^^^^^^^^^^^^^^^^^^^^^^^^
- NOTE NEW EMAIL ADDRESS