[R] Subsetting a data frame by a factor, using the level that occurs the most times

[michael watson (IAH-C)]

I think that title makes sense... I hope it does...

I have a data frame, one of the columns of which is a factor.  I want
the rows of data that correspond to the level in that factor which
occurs the most times.  

I can get a list by doing:

by(data,data$pattern,subset)

And go through each element of the list counting the rows, to find the
maximum....

BUT I can't help thinking there's a more elegant way of doing this....

The second part is figuring out the rows which have the maximum number
of consecutive patterns which are the same... Now that I would love some
help with... :-)

Thanks
Mick