How to display jFree chart for a table of values vs Time taken

Question

I was trying to display values like Heartrate,blood pressure vs time taken.
How can I display like a bar graph using JFree chart??
Getting a NullPointerException in my for loop

private CategoryDataset createDataset(VitalSignDirectory vitalSignDirectory) {
    DefaultCategoryDataset dataset = new DefaultCategoryDataset();

    for(VitalSign v : patient.getVitalSignDirectory().getVitalSignList()) {
        String heartRate = String.valueOf(v.getHeartRate());


        dataset.addValue(v.getRespRate(), heartRate, heartRate);
    }
    return dataset;
}

Answer 1

Have a look at this link showing how to create a time/value bar graphs.

The key point being that data should be added as

TimeSeries s1 = new TimeSeries("Series 1", Month.class);
s1.add(new Month(1, 2001), 142);
s1.add(new Month(2, 2001), 181);