报告趋势线

Question

除了显示数据点之外，如何在 JasperReports 中创建一条遵循数据趋势的线？以下是之前和之后的照片：

之前

之后

时间序列报告似乎没有任何此类选项来绘制橙色线。 （橙色线应该是平滑且细的，但这是总体思路。）

有什么想法如何使用 iReport 3.7.1 制作这样的报告吗？

Answer 1

一种解决方案需要以下项目：

• BezierLineCustomizer 使线条弯曲。
• RunningAverageIncrementer 用于计算基于变量的运行平均值。
• 使用 RunningAverageIncremeter 的 iReport 变量。

BezierLineCustomizer 类

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 );
  }
}

RunningAverageIncrementer 类

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 变量

创建一个使用 RunningAverageIncrementerFactory 类的变量（留给读者练习）。将其变量表达式设置为绘制的值。将其初始值表达式设置为零。

Spline

设置 TimeSeries 图表的 Customizer Class 属性以使用 BezierLineCustomizer 类。

结果

经过这些修改，运行平均值清晰可见：