Formatting axis with decimals dynamically for JFreeChart

Question

I am trying to format the y-axis of charts I am creating (JFreeCharts)

DecimalFormat df = new DecimalFormat("0", DecimalFormatSymbols.getInstance(Locale.ENGLISH));
df.setMaximumFractionDigits(5); 
numberTickUnit = new NumberTickUnit(numberTickUnit.getSize(), df);

Some charts have a range from say 0-15, so I want the numbers to have 2 decimals. Some charts have a range from 0.001 to 0.002, so I want the numbers to have 5 decimals.

The code above works well, with 1 issue. I want all the numbers on the axis to have the same format (the maximum number of decimals). So if I have 0.01251, 0.02000, 0.27490, I want it to display like that, as opposed to 0.01251, 0.02, 0.2749. How do I make the entire axis have the same format, instead of setting it separately for each number.

Have you tried `NumberAxis::setNumberFormatOverride`, for [example](http://stackoverflow.com/a/33595830/230513)? — trashgod, Jun 21 '16 at 18:42
@trashgod Yes, but each number is still formatted differently. — user101, Jun 21 '16 at 19:22

score 2 · Answer 1 · answered Jun 22 '16 at 03:49

2

I want the numbers to have 5 decimals.

Use setMinimumFractionDigits(), which "Sets the minimum number of digits allowed in the fraction portion of a number."

XYPlot plot =  (XYPlot) chart.getPlot();
NumberAxis range = (NumberAxis) plot.getRangeAxis();
NumberFormat formatter = DecimalFormat.getInstance();
formatter.setMinimumFractionDigits(5);
range.setNumberFormatOverride(formatter);

answered Jun 22 '16 at 03:49

trashgod

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Sorry, I was unclear. The number of decimals should vary based on the range. – user101 Jun 24 '16 at 19:36

score 1 · Accepted Answer · edited Jun 24 '16 at 20:13

I had to do it manually.

static NavigableMap<Double, String> decimalFormatMap = new TreeMap<Double, String>();
static
{
    decimalFormatMap.put(0.00001, "0.000001");
    decimalFormatMap.put(0.0001, "0.00001");
    decimalFormatMap.put(0.001, "0.0001");
    decimalFormatMap.put(0.01, "0.001");
    decimalFormatMap.put(0.1, "0.01");
    decimalFormatMap.put(1.0, "0.1");
    decimalFormatMap.put(100.0, "1");
}
NumberTickUnit numberTickUnit = * some key number *;
String decimalFormat = decimalFormatMap.get(
    decimalFormatMap.floorKey(numberTickUnit.getSize()));

Formatting axis with decimals dynamically for JFreeChart

2 Answers2