possible minor bug in fisher.test

Hi,

I received a bug report for my exact2x2 package that seems to apply to fisher.test in the stats package also.

Here is some code which creates the error:

x<-factor(c(0,1,1),levels=c(0,1))
y<-factor(c(1,1,1),levels=c(0,1))
fisher.test(x,y)

Error in fisher.test(x, y) : 'x' and 'y' must have at least 2 levels

The help says that x and y could be factors, and technically y does have 2 levels, although both are not observed. There is no problem statistically with y not having 2 observed levels,  and

fisher.test(table(x,y))

Produces the correct p-value of 1 and no errors.

There is an easy solution. In fisher.test replace

       x <- factor(x[OK])
       y <- factor(y[OK])


with

       x <- as.factor(x[OK])
       y <- as.factor(y[OK])

(similar to how it is done in mcnemar.test).