\begin{Schunk}
\begin{Sinput}
  levels(x) <- c(levels(x), "BorC")
  x[ x %in% c("B", "C")] <- "BorC"
  x <- factor(x)
  table(x)
\end{Sinput}
\begin{Soutput}
x
   A BorC 
   1    4 
\end{Soutput}
\end{Schunk}
