\begin{Schunk}
\begin{Sinput}
 t1 <- with(dat, table(gunlaw, owngun, exclude=NULL) )
 t1.prop <- 100 * prop.table(t1, margin=2)
 t1.prop <- round(t1.prop, 1)
 t1.prop
\end{Sinput}
\begin{Soutput}
        owngun
gunlaw    YES   NO REFUSED <NA>
  FAVOR  69.9 83.0    56.7  0.1
  OPPOSE 28.9 14.8    33.3  0.0
  <NA>    1.2  2.2    10.0 99.9
\end{Soutput}
\end{Schunk}
