Trend reporting line

Question

How would you create a line in JasperReports that follows the data trend, in addition to displaying data points? Here are the before and after pictures:

Before

After

The Time Series report does not seem to have the ability to draw an orange line. (The orange line should be smooth and thinner, but the general idea.)

Any ideas on creating such a report using iReport 3.7.1?

Answer 1

One solution requires the following elements:

• BezierLineCustomizer to make lines curved.
• RunningAverageIncrementer to calculate the average value based on a variable.
• iReport variable using RunningAverageIncremeter .

BezierLineCustomizer Class

 public class BezierLineCustomizer implements JRChartCustomizer { public BezierLineCustomizer() { } public void customize( JFreeChart jFreeChart, JRChart jrChart ) { XYPlot xyPlot = ( XYPlot )jFreeChart.getPlot(); XYSplineRenderer splineRenderer = new XYSplineRenderer(); // Make the spline line thick and orange. // splineRenderer.setSeriesShapesVisible( 0, false ); splineRenderer.setSeriesShapesVisible( 1, false ); splineRenderer.setSeriesLinesVisible( 1, false ); splineRenderer.setSeriesStroke( 0, new BasicStroke( 4.0f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND, 1.0f, null, 0.0f ) ); splineRenderer.setSeriesPaint( 0, new Color( 255, 140, 0 ) ); splineRenderer.setSeriesVisibleInLegend( 1, Boolean.FALSE ); // Duplicate the data into a new dataset to control its line independently. // xyPlot.setDataset( 1, xyPlot.getDataset(0) ); XYItemRenderer defaultRenderer = new XYLineAndShapeRenderer(); defaultRenderer.setSeriesVisible( 0, Boolean.FALSE ); defaultRenderer.setSeriesVisibleInLegend( 0, Boolean.FALSE ); xyPlot.setRenderer( 1, defaultRenderer ); xyPlot.setRenderer( 0, splineRenderer ); } } 

Class RunningAverageIncrementer

 public class RunningAverageIncrementer implements JRIncrementer { /** Default number of tallies. */ private static final int DEFAULT_TALLIES = 128; /** Number of tallies within the sliding window. */ private static final int DEFAULT_SLIDING_WINDOW_SIZE = 30; /** Stores a sliding window of values. */ private List<Double> values = new ArrayList<Double>( DEFAULT_TALLIES ); /** * Instantiated by the RunningAverageIncrementerFactory class. */ public RunningAverageIncrementer() { } /** * Calculates the average of previously known values. * @return The average of the list of values returned by getValues(). */ private double calculateAverage() { double result = 0.0; List<Double> values = getValues(); for( Double d: getValues() ) { result += d.doubleValue(); } return result / values.size(); } /** * Called each time a new value to be averaged is received. * @param value The new value to include for the average. */ private void recordValue( Double value ) { List<Double> values = getValues(); // Throw out // if( values.size() > getSlidingWindowSize() ) { values.remove( 0 ); } this.values.add( value ); } private List<Double> getValues() { return values; } private int getIterations() { return getValues().size(); } /** * Returns the newly incremented value, which is calculated by averaging * the previous value from the previous call to this method. * * @param jrFillVariable Unused. * @param tally New data point to average. * @param abstractValueProvider Unused. * @return The newly incremented value. */ public Object increment( JRFillVariable jrFillVariable, Object tally, AbstractValueProvider abstractValueProvider ) { double value = ((Number)tally).doubleValue(); recordValue( value ); double previousAverage = calculateAverage(); double newAverage = ( ( value - previousAverage ) / ( getIterations() + 1 ) ) + previousAverage; return new BigDecimal( newAverage ); } protected int getSlidingWindowSize() { return DEFAULT_SLIDING_WINDOW_SIZE; } } 

iReport Variable

Create a variable that uses the RunningAverageIncrementerFactory class (exercise to the left of the reader). Set the variable expression to the constructed value. Set its initial value to zero.

Spline

Set the TimeSeries chart class property property to use the BezierLineCustomizer class.

Result

After these changes, the average mileage is clearly visible: