[R] getting line breaks with xtable

[Erich Studerus]

Sorry, for asking the same question again, but I got no reactions the last
time. Maybe it was just overseen by the experts.
I'm using the xtable function with Sweave and Lyx and I would like to know
how to get automatic line breaks for long strings in a column of the table.
I've learned from the Lyx wiki that the Latex command \linebreak produces
table cells with multiple lines. I tried to insert \linebreak into the
character string, but it didn't work out, because Sweave transforms it
automatically to $\backslash$linebreak. 

Any help is highly appreciated.

Erich