The AxisValueFormatter interface

Introduced in release v3.0.0, this interface allows the custom styling of both XAxis and YAxis values before drawing.

Creating a Formatter

All that needs to be done to custom-format values on the axis is to create a class that implements the IAxisValueFormatter interface, as shown below. This formatter is used to format the values of an axis to 1 decimal digit always.

public class MyYAxisValueFormatter implements IAxisValueFormatter {

    private DecimalFormat mFormat;

    public MyAxisValueFormatter() {

        // format values to 1 decimal digit
        mFormat = new DecimalFormat("###,###,##0.0");
    }

    @Override
    public String getFormattedValue(float value, AxisBase axis) {
        // "value" represents the position of the label on the axis (x or y)
        return mFormat.format(value) + " $";
    }
    
    /** this is only needed if numbers are returned, else return 0 */
    @Override
    public int getDecimalDigits() { return 1; }
}

The example below shows how to plot values from a String[] array to the axis:

public class MyXAxisValueFormatter implements IAxisValueFormatter {

    private String[] mValues;

    public MyXAxisValueFormatter(String[] values) {
        this.mValues = values;
    }

    @Override
    public String getFormattedValue(float value, AxisBase axis) {
        // "value" represents the position of the label on the axis (x or y)
        return mValues[(int) value];
    }
    
    /** this is only needed if numbers are returned, else return 0 */
    @Override
    public int getDecimalDigits() { return 0; }
}

Setting the Formatter

After the creation of the formatter, simply set it to your axis of choice:

YAxis left = chart.getAxisLeft();
left.setValueFormatter(new MyYAxisValueFormatter());

String[] values = new String[] { ... };

XAxis xAxis = chart.getXAxis();
xAxis.setValueFormatter(new MyXAxisValueFormatter(values));

Instead of the default values ranging from axis minimum value to axis maximum value, the axis will now plot the data specified by the formatter.

Restricting Intervals

In case you are using a formatter based on array indices (like above), it makes sense to restrict the minimum interval of your axis to "1":

axis.setGranularity(1f); // restrict interval to 1 (minimum)

This will prevent the formatter from drawing duplicate axis labels (caused by axis intervals < 1). As soon as the "zoom level" of the chart is high enough, it will stop recalculating smaller intervals.

Predefined Formatters

• LargeValueFormatter: Can be used for formatting large values > "1.000". It will turn values like "1.000" into "1k", "1.000.000" will be "1m" (million), "1.000.000.000" will be "1b" (billion) and values like one trillion will be e.g. "1t".
• PercentFormatter: Used for displaying a "%" sign after each value with 1 decimal digit. Especially useful for the PieChart. 50 -> 50.0 %

Example Formatters

• DayAxisValueFormatter: This formatter converts the provided value to plot into a date String, altering the string depending on scale.

Legacy Formatters

Prior to release v3.0.0, there were separate formatters for XAxis and YAxis. The documentation for these formatters can be found here:

• XAxisValueFormatter
• YAxisValueFormatter