How can I remove old data in MPAndroidChart?

Question

Hi this is my code but not work (newest version of library)

LineData dataChart = mainChart.getData();

    if (dataChart != null) {

        LineDataSet set = (LineDataSet) dataChart.getDataSetByIndex(0);
        if (set == null) {
            set = (LineDataSet) createSet(ColorTemplate.rgb(colorChart), ColorTemplate.rgb(colorFill));
            dataChart.addDataSet(set);
        }



        dataChart.addEntry(new Entry(set.getEntryCount(), sensorEvent.values[2]), 0);
        dataChart.notifyDataChanged();

        if(set.getEntryCount() == 20) {
            set.removeFirst();
        }

        // let the chart know it's data has changed
        mainChart.notifyDataSetChanged();
        // limit the number of visible entries
        mainChart.setVisibleXRangeMaximum(20);
        mainChart.moveViewToX(dataChart.getEntryCount());

    }

`output of this cod: not correct

but when I chang my code:

LineData dataChart = mainChart.getData();

    if (dataChart != null) {

        LineDataSet set = (LineDataSet) dataChart.getDataSetByIndex(0);
        if (set == null) {
            set = (LineDataSet) createSet(ColorTemplate.rgb(colorChart), ColorTemplate.rgb(colorFill));
            dataChart.addDataSet(set);
        }



        dataChart.addEntry(new Entry(set.getEntryCount(), sensorEvent.values[2]), 0);
        dataChart.notifyDataChanged();

        // let the chart know it's data has changed
        mainChart.notifyDataSetChanged();
        // limit the number of visible entries
        mainChart.setVisibleXRangeMaximum(300);
        mainChart.moveViewToX(dataChart.getEntryCount());

    }

and the output is correct,so what should I do to remove old data from the chart? correct but I want delet old data

Answer 1

I found some issues in previous answers. So, I tried different approach.

Advantages: 1. Entry count of the dataset remains constant. 2. A real-time graph like ECG

private long removalCounter = 0;
private static final int VISIBLE_COUNT = 300;

private void addNewEntry(double value) {

    LineData data = lineChart.getData();

    if (data != null) {

        ILineDataSet set = data.getDataSetByIndex(0);

        if (set == null) {
            set = createDataSet();
            data.addDataSet(set);
        }

        data.addEntry(new Entry(set.getEntryCount() + removalCounter, (float) value), 0);
        data.notifyDataChanged();

        // limit the number of visible entries
        lineChart.setVisibleXRangeMaximum(VISIBLE_COUNT);

        // move to the latest entry
        lineChart.moveViewToX(set.getEntryCount());

        //remove entry which is out of visible range 
        if (set.getEntryCount() > VISIBLE_COUNT){
            data.removeEntry(removalCounter, 0);
            removalCounter++;
        }
        lineChart.notifyDataSetChanged();
    }
}


private LineDataSet createDataSet() {

    LineDataSet set = new LineDataSet(null, "real_time");
    set.setAxisDependency(YAxis.AxisDependency.LEFT);
    set.setColor(Color.RED);
    set.setLineWidth(1f);
    set.setDrawCircles(false);
    set.setHighlightEnabled(false);
    set.setDrawValues(false);
    set.setMode(LineDataSet.Mode.HORIZONTAL_BEZIER);
    set.setCubicIntensity(0.2f);
    return set;
}

Answer 2

Solution for v3.0.2 of MPAndroidChart from this answer of Adam Wu:

if (set.getEntryCount() >= MAX_ENTRIES) {  
    set.removeFirst();    
    for (int i=0; i<set.getEntryCount(); i++) {  
        Entry entryToChange = set.getEntryForIndex(i);  
        entryToChange.setX(entryToChange.getX() - 1);  
    }  
}

Answer 3

The problem was solved. I should add this lines.

if(set.getEntryCount() == MAX_ENTRIES) {
            set.removeFirst();
            // change Indexes - move to beginning by 1
            for (Entry entry : set.getValues() )
                entry.setX(entry.getX() - 1);
}

Answer 4

I also had this problem.I want to show the last 5 entries in a LineChart,so when a data is comming,I call addXValue() and addEntry().Since the entry count is 5,I call removeXValue(0) and removeEntry(0) to remove the oldest entry,but the LineChart is very strange:in fact the entry count is 5,but it only one entry in the end,now I don't know how to do with it.Here is my code:

private static final int VISIBLE_NUM = 5;

private void refreshData(float value) {
    LineData data = mChart.getData();
    if (data != null) {
        LineDataSet set = data.getDataSetByIndex(0);

        if (set == null) {

            set = new LineDataSet(null, "DataSet");
            set.enableDashedLine(10f, 5f, 0f);
            set.setColor(Color.BLUE);
            set.setCircleColor(Color.GREEN);
            set.setLineWidth(1f);
            set.setCircleSize(3f);
            set.setDrawCircleHole(false);
            set.setValueTextSize(9f);
            set.setFillAlpha(65);
            set.setFillColor(Color.BLACK);

            data.addDataSet(set);
        }

        if(set.getEntryCount() == VISIBLE_NUM) {
            data.removeXValue(0);
            set.removeEntry(0);
        }

        data.addXValue(new SimpleDateFormat("HH:mm:ss")
                .format(new Date(System.currentTimeMillis())));
        data.addEntry(new Entry(value, set.getEntryCount()), 0);

        mChart.notifyDataSetChanged();
        //mChart.setVisibleXRange(VISIBLE_NUM-1);
        //mChart.moveViewToX(data.getXValCount() - VISIBLE_NUM);
        mChart.invalidate();
    }

}