平线而不是波浪

Question

我想绘制一个正弦波，但我的应用程序生成了一条平面线。当我使用jchartfree示例中的随机序列时，一切都很好。我还使用调试器来检查值是否正确。值不同于零

public void createDataset() {
    XYSeriesCollection dataset = new XYSeriesCollection();
    XYSeries series1 = new XYSeries("Object 1");
    double A = 1;                       
    double T = 1;                       
    double Fs = 10;                   
    double f = 200;                     
    int rozmiar = (int) (T*Fs);
    double[] x = new double[rozmiar];
   for (int i = 0; i < rozmiar; i++)
   {
        x[i] = A * Math.sin(2 * Math.PI * f * i / Fs);
        series1.add(i, x[i]);
   }
    dataset.addSeries(series1);
    data = dataset;
}
//...
public void createChartPanel() {
    //pWykres = new JPanel();
    //if(java.util.Arrays.asList(getComponents()).contains(pWykres)){
        //getContentPane().remove(pWykres);
    //}
    if(pWykres != null){
        pWykres.removeAll();
        pWykres.revalidate();
    }
    String chartTitle = "Objects Movement Chart";
    String xAxisLabel = "X";
    String yAxisLabel = "Y";
    JFreeChart chart = ChartFactory.createXYLineChart(chartTitle,
            xAxisLabel, yAxisLabel, dataset);
    customizeChart(chart);
    pWykres = new ChartPanel(chart);
    getContentPane().add(pWykres, BorderLayout.CENTER);
    setSize(620, 460);
    //validate();
    pWykres.repaint();
}
//endregion
//...    
//region 
private void customizeChart(JFreeChart chart) {
    XYPlot plot = chart.getXYPlot();
    XYSplineRenderer renderer;
            renderer = new XYSplineRenderer();
            renderer.setSeriesShapesVisible(0, false);
    // sets paint color for each series
    renderer.setSeriesPaint(0, Color.RED);
    // sets thickness for series (using strokes)
    renderer.setSeriesStroke(0, new BasicStroke(1.0f));
    // sets paint color for plot outlines
    //plot.setOutlinePaint(Color.BLUE);
    //plot.setOutlineStroke(new BasicStroke(2.0f));
    // sets renderer for lines
    plot.setRenderer(renderer);
    // sets plot background
    plot.setBackgroundPaint(Color.WHITE);
    // sets paint color for the grid lines
    plot.setRangeGridlinesVisible(true);
    plot.setRangeGridlinePaint(Color.BLACK);
    plot.setDomainGridlinesVisible(true);
    plot.setDomainGridlinePaint(Color.BLACK);
}

Answer 1

您所取的值的正弦值始终是2 * PI的整数倍，因此所有这些值都将（近似）为零，因此您的图形最终将显示为平面，除非对其进行缩放以显示这些微小值（这些值只是浮点误差）。

x[i] = A * Math.sin(2 * Math.PI * f * i / Fs);

其中A＝1且f/Fs＝20且i为整数

例如：

Math.sin(0)             // 0.0
Math.sin(2 * Math.PI)   // -2.4492935982947064E-16  (approximately zero)
Math.sin(4 * Math.PI)   // -4.898587196589413E-16   (approximately zero)

要查看正弦波的特征形状，需要以更小的增量改变sin函数的输入，例如π/10或更小。