}
\arguments{
\item{x}{x location of the bar (can be left missing).}
\item{y}{y location of the bar (can be left missing).}
\item{length}{a numeric value giving the length of the scale bar. If
none is supplied, a value is calculated from the data.}
}
\arguments{
\item{x}{x location of the bar (can be left missing).}
\item{y}{y location of the bar (can be left missing).}
\item{length}{a numeric value giving the length of the scale bar. If
none is supplied, a value is calculated from the data.}