How do I round to two decimal places on MPAndroidChart? - rounding

Question

I've made a line chart on MPAndroidChart and would like the output to only show two decimal places.
This is the code I've used to round off the data. The data was originally in a Long ArrayList. I converted it to float because Android Studio wanted it to be in float.
private static final DecimalFormat df = new DecimalFormat("0.00");
ArrayList<Entry> dataVals = new ArrayList<Entry>();
for (i=0; i<sampleSize; i++){
float k = list.get(i)/1000;
df.setRoundingMode(RoundingMode.UP);
df.format(k);
dataVals.add(new Entry((float) (i), k));
}
The datapoints sometimes show two decimal places and sometimes three. I can't work out why.
Does anyone know how to ensure it always rounds off to decimal places?

Answer 1

// Create a custom ValueFormatter that rounds to two decimal places
ValueFormatter formatter = new ValueFormatter() {
#Override
public String getFormattedValue(float value) {
return String.format(Locale.getDefault(), "%.2f", value);
}
};
// Set the ValueFormatter on the chart
chart.getAxisLeft().setValueFormatter(formatter);

Answer 2

If you want to control the formatting of the numbers displayed over each data point, you have to define a value formatter on the data set (not the axis - which controls the format of the numbers on the chart axes). For example, to show 2 decimal places for all points, you would add this (using your existing decimal formatter df):
dataSet.setValueFormatter(new ValueFormatter() {
#Override
public String getFormattedValue(float value) {
return df.format(value);
}
});
A more complete example:
// declare the formatter as a class member
private static final DecimalFormat df = new DecimalFormat("0.00");
// Prepare your list of Entries (no need to do anything with the
// formatter here)
ArrayList<Entry> dataVals = new ArrayList<Entry>();
for (i=0; i<sampleSize; i++){
float k = list.get(i)/1000;
dataVals.add(new Entry((float) (i), k));
}
// set the formatter mode (only need to call this once,
// not inside the loop)
df.setRoundingMode(RoundingMode.UP);
// create a LineDataSet from your list of entries
LineDataSet dataSet = new LineDataSet(dataVals, "Values");
// Set a value formatter on the data set (to control
// how the numbers over the points are shown) and
// call your data formatter here
dataSet.setValueFormatter(new ValueFormatter() {
#Override
public String getFormattedValue(float value) {
return df.format(value);
}
});
Note You can also define this formatter on the LineData object instead of the LineDataSet if you have multiple data sets and want to apply the same formatter to all of them. The syntax is the same as setting it on the LineDataSet.
LineData data = new LineData(dataSet);
data.setValueFormatter(new ValueFormatter() {
#Override
public String getFormattedValue(float value) {
return df.format(value);
}
});