Using dates with the Graphview library

Question

I'm using GraphView library (see: https://github.com/jjoe64/GraphView or http://www.jjoe64.com/p/graphview-library.html)

But I would like to use Date/Time for the X-as. Does anyone knows a easy way to accomplish this or can anyone push me in the right direction?

Answer 1

I created the horizontal labels at the same time I was setting the values:

public void initializeLineGraphView() {

    // Get last weeks entries from the DB
    ArrayList<Entry> entries = DbManager.getInstance().getLastWeeksEntries(new Date());
    String[] hLabels = new String[entries.size()];
    GraphView.GraphViewData[] graphViewData = new GraphView.GraphViewData[entries.size()];

    for(int i = 0; i < entries.size(); i++) {

        Entry entry = entries.get(i);
        int pain = entry.getPain();
        graphViewData[i] = new GraphView.GraphViewData(i, pain);

        // Generate the horizontal labels
        SimpleDateFormat sdf = new SimpleDateFormat("EEE");
        String dayOfWeek = sdf.format(entry.getDate());
        hLabels[i] = dayOfWeek;

    }

    mSeries = new GraphViewSeries("", null, graphViewData);
    GraphView graphView = new LineGraphView(getActivity(), "");
    graphView.addSeries(mSeries);
    graphView.setHorizontalLabels(hLabels);
    graphView.setVerticalLabels(new String[] {"10", "5", "0"});
    mLineGraphView = graphView;

}

Answer 2

This is the correct way to do this

You just have to use the unix timestamp (seconds from 1.01.1970) as x value.

Then you can set a custom label formatter and convert the unix timestamp to a String:

final java.text.DateFormat dateTimeFormatter = DateFormat.getTimeFormat(mActivity);

LineGraphView graphView = new LineGraphView(mActivity, entry.getValue()) {
    @Override
    protected String formatLabel(double value, boolean isValueX) {
        if (isValueX) {
            // transform number to time
            return dateTimeFormatter.format(new Date((long) value*1000));
        } else {
            return super.formatLabel(value, isValueX);
        }
    }
};

Answer 3

Here's the updated answer from jjoe64, with the x-values obtained from Date#getTime()

    final DateFormat dateTimeFormatter = DateFormat.getDateTimeInstance();        
    graphView = new LineGraphView(context, "Chart");
    graphView.setCustomLabelFormatter(new CustomLabelFormatter() 
    {
        @Override
        public String formatLabel(double value, boolean isValueX) 
        {
            if (isValueX)
            {
                return dateTimeFormatter.format(new Date((long) value));
            }
            return null; // let graphview generate Y-axis label for us
        }
    });

Answer 4

GraphView is a great library to use, i find it the easiest as well. The first step in doing this would be to add a String Variable in the GraphViewData Class within GraphView.java. Like So:

static public class GraphViewData {
    public final double valueX;
    public final double valueY;
    public final String valueDate;

    public GraphViewData(double valueX, double valueY,String valueDate) {
        super();
        this.valueX = valueX;
        this.valueY = valueY;
        this.valueDate = valueDate;
    }
}

When you create your GraphViewData object when creating a GraphView Graph, you will need to add the date data in string form (along with the X and Y).

Lets say you have 80 data points in your graph (index 0 - 79). There is a method within GraphView that is responsible for generating and returning the horizontal labels, i believe its called generateHorLabels. Instead of just returning the X Value (0-79), Use the X value to get the String from the GraphData object.

In the code you have now, it should have the following in a for loop

labels[i] = formatLabel(min + ((max-min)*i/numLabels), true);

instead of the above, you could do something like this.

Double temp =  Double.valueOf(formatLabel(min + ((max-min)*i/numLabels), true));
int rounded =(int)Math.round(temp); 
labels[i] = values[rounded].valueDate;

Hope this helped!