*/
public int getDomainAxisIndex(final ValueAxis axis) {
int result = this.domainAxes.indexOf(axis);
if (result < 0) {
// try the parent plot
final Plot parent = this.getParent();
if (parent instanceof XYPlot) {
final XYPlot p = (XYPlot) parent;
result = p.getDomainAxisIndex(axis);
}
}