少し古い質問ですが、極座標プロットを使用して同様のこと(1、2、3、...時の位置に注釈)を行う方法を次に示します。ChoiceFormatter と NumberTickUnit を使用します。
final JFreeChart chart = ChartFactory.createPolarChart(
"HAPI Hourly Usage (UTC)", ds, true, true, false);
final PolarPlot plot = (PolarPlot) chart.getPlot();
// Create a ChoiceFormat to map the degrees to clock positions
double[] limits = new double[12];
String[] formats = new String[12];
limits[0] = 0;
formats[0] = "12";
// degrees = 360/12
for (int i = 1; i < limits.length; i++) {
limits[i] = degrees * (i);
formats[i] = Integer.toString(i);
}
ChoiceFormat clock = new ChoiceFormat(limits, formats);
TickUnit tickUnit = new NumberTickUnit(degrees, clock);
// now configure the plot
plot.setAngleTickUnit(tickUnit); // sets the ticks
plot.setAngleLabelsVisible(true); // makes the labels visible
plot.setAngleLabelPaint(Color.LIGHT_GRAY); // user choice
plot.setAngleGridlinesVisible(true); // must set this to display the
// labels
plot.setAngleGridlinePaint(Color.BLACK); // plot's background color
// (makes lines invisible)
plot.setRadiusGridlinesVisible(false); //turn off the radius value circles
ValueAxis axis = plot.getAxis();
axis.setTickLabelsVisible(false); //turn off the radius value labels
http://img522.imageshack.us/img522/6693/hapihours.jpgのようになります