legend.loc places a legend into one of nine locations on the chart: bottomright, bottom, bottomleft, left, topleft, top, topright, right, or center.

character vector of names for the legend. If NULL, the column names of the current plot object are used.

fill colors for the legend. If NULL, the colorset of the current plot object data is used.

number of columns for the legend

panel number to draw on. A new panel will be drawn if on=NA. The default, on=0, will add to the active panel. The active panel is defined as the panel on which the most recent action was performed. Note that only the first element of on is checked for the default behavior to add to the last active panel.

any other passthrough parameters to legend.