WPF随笔（八）--使用LiveCharts创建散点图

最近遇到一个绘制散点图用来做数据分析的需求，正好最近了解过开源图表控件LiveCharts，刚好拿来试一试。

简单实例

新建WPF应用程序，使用NuGet安装LiveCharts.Wpf类库。

在XAML代码中添加LiveCharts.Wpf的引用并增加一个图表控件。

<Window x:Class="ChartDemo.WPF.MainWindow"
                      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                   xmlns:lvc="clr-namespace:LiveCharts.Wpf;assembly=LiveCharts.Wpf"
                      Title="MainWindow" Height="720" Width="1280">
    <Grid Margin="5">
        <Grid.RowDefinitions>
            <RowDefinition Height="50">RowDefinition>
            <RowDefinition>RowDefinition>
        Grid.RowDefinitions>
        <Border Grid.Row="0">
            <WrapPanel VerticalAlignment="Center" HorizontalAlignment="Center">
                <Button x:Name="btnTest" Click="btnTest_Click">查看图表Button>
            WrapPanel>
        Border>
        <Border Grid.Row="1">
            <lvc:CartesianChart x:Name="lvcChart">
            lvc:CartesianChart>
        Border>
    Grid>
Window>

最简单的一个图表控件就添加完成了，下面是在后台代码中为图表控件添加数据源。数据源从Excel表格中读取，所以引用了Aspose.Cells用来读取Excel表格。

        private void btnTest_Click(object sender, RoutedEventArgs e)
        {
            System.Windows.Forms.OpenFileDialog dialog = new System.Windows.Forms.OpenFileDialog();
            dialog.Filter = "Excel 2007(*.xlsx)|*.xlsx";
            System.Windows.Forms.DialogResult result = dialog.ShowDialog();
            if (result == System.Windows.Forms.DialogResult.OK)
            {

                try
                {
                    string fileName = dialog.FileName;
                    if (string.IsNullOrEmpty(fileName))
                    {
                        return;
                    }
                    Workbook book = new Workbook(fileName);
                    Worksheet sheet = book.Worksheets[0];
                    Cells cells = sheet.Cells;
                    //初始化数据序列集合
                    SeriesCollection collection = new SeriesCollection();
                    //初始化数据序列
                    ScatterSeries series = new ScatterSeries()
                    {
                        Values = new ChartValues<ScatterPoint>()
                    };
                    for (int i = 1; i < cells.MaxDataRow; i++)
                    {
                        double x = 0;
                        double y = 0;
                        if (cells.GetCell(i, 1) == null || cells.GetCell(i, 2) == null)
                        {
                            continue;
                        }
                        x = cells.GetCell(i, 1).DoubleValue;
                        y = cells.GetCell(i, 2).DoubleValue;
                        ScatterPoint point = new ScatterPoint(x, y);
                        series.Values.Add(point);
                    }
                    collection.Add(series);
                    this.lvcChart.Series = collection;
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }
        }
    }

这样一个简单的散点图就完成了，效果如下：

功能进阶

在上一步用很少的代码就实现了图表绘制，但现在的图表未免有些单调了，能否更高级一些呢？

1.对Y值进行划分并显示不同背景

            <lvc:CartesianChart x:Name="lvcChart">
                <lvc:CartesianChart.AxisY>
                    <lvc:Axis>
                        <lvc:Axis.Sections>
                            
                            <lvc:AxisSection Value="4" SectionWidth="16" Label="区间2">
                                <lvc:AxisSection.Fill>
                                    <SolidColorBrush Color="#CDCDCD" Opacity=".4">SolidColorBrush>
                                lvc:AxisSection.Fill>
                            lvc:AxisSection>
                            <lvc:AxisSection Value="0" SectionWidth="4" Label="区间1">
                                <lvc:AxisSection.Fill>
                                    <SolidColorBrush Color="#FF8585" Opacity=".4">SolidColorBrush>
                                lvc:AxisSection.Fill>
                            lvc:AxisSection>
                        lvc:Axis.Sections>
                    lvc:Axis>
                lvc:CartesianChart.AxisY>
            lvc:CartesianChart>

效果如下：

2.同时对X、Y值进行划分并显示不同颜色的点

上一步通过划分Y值区间显示不同的区域背景很容易实现，但如何让不同区间的点显示不同颜色或图形呢？这个就要从数据上着手，在后台代码中事先将不同的区间的值放到不同的数据序列中，然后赋予数据序列不同的形状和颜色。

private void btnTest_Click(object sender, RoutedEventArgs e)
{
    System.Windows.Forms.OpenFileDialog dialog = new System.Windows.Forms.OpenFileDialog();
    dialog.Filter = "Excel 2007(*.xlsx)|*.xlsx";
    System.Windows.Forms.DialogResult result = dialog.ShowDialog();
    if (result == System.Windows.Forms.DialogResult.OK)
    {
        try
        {
            string fileName = dialog.FileName;
            if (string.IsNullOrEmpty(fileName))
            {
                return;
            }
            Workbook book = new Workbook(fileName);
            Worksheet sheet = book.Worksheets[0];
            Cells cells = sheet.Cells;
            SeriesCollection collection = new SeriesCollection();
            ScatterSeries seriesLeft = new ScatterSeries()
            {
                Values = new ChartValues<ScatterPoint>(),
                PointGeometry = DefaultGeometries.Square,
                Fill = new SolidColorBrush(Colors.OrangeRed)
            };
            ScatterSeries seriesRight = new ScatterSeries()
            {
                Values = new ChartValues<ScatterPoint>(),
                Fill = new SolidColorBrush(Colors.LimeGreen)
            };
            ScatterSeries seriesBottom = new ScatterSeries()
            {
                Values = new ChartValues<ScatterPoint>(),
                PointGeometry = DefaultGeometries.Triangle
            };
            for (int i = 1; i < cells.MaxDataRow; i++)
            {
                double x = 0;
                double y = 0;
                if (cells.GetCell(i, 1) == null || cells.GetCell(i, 2) == null)
                {
                    continue;
                }
                x = cells.GetCell(i, 1).DoubleValue;
                y = (Math.Log10(cells.GetCell(i, 2).DoubleValue)) * (-1);
                if (y > 2 && x < -0.3)
                {
                    ScatterPoint point = new ScatterPoint(x, y);

                    seriesLeft.Values.Add(point);
                }
                else if (y > 2 && x > 3)
                {
                    ScatterPoint point = new ScatterPoint(x, y);
                    seriesRight.Values.Add(point);
                }
                else
                {
                    ScatterPoint point = new ScatterPoint(x, y);
                    seriesBottom.Values.Add(point);
                }
            }
            collection.Add(seriesLeft);
            collection.Add(seriesRight);
            collection.Add(seriesBottom);
            this.lvcChart.Series = collection;
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }
}

效果如下图所示：

---

以上只是LiveCharts的一部分功能，更多的功能可以到官网去探索。对比以前用过的WPF图表控件vsfire、ModernUIChart和DevExpress，界面好过vsfire但缺少保存图片的功能，界面与MordenUIChart相当但是图表类型稍微丰富些，功能不如DevExpress丰富但是开源啊。
各有千秋，选择合适的就好。