c# - 使用 C# 从图形数据中删除插值点

Question

给定文件中的两列图形数据，我正在读取文件内容并将值存储在 ArrayList,How to "un-interpolate",

即压缩到生成相同折线图的最少行数。

举个简单的例子:

x    y
1    2
2    5
3    8
4    6
5   -1
6   -2
7    4 

会变成:

x    y
1    2
3    8
6   -2
7    4 

因为这会产生相同的折线图，删除了两条直线上的“中间”点。

有人可以指导我如何使用 C# 实现这一目标吗？

Answer 1

应该有一些更优雅的解决方案，但我们开始吧:

List<Point> reducePlotLines(List<Point> points)
{
    float limit = 0.1f;

    List<Point> newPoints = new List<Point>();
    Dictionary<int, float> slopes = new Dictionary<int, float>();
    List<int> toRemove = new List<int>();

    for (int i = 1; i < points.Count; i++)
    {
        if ( points[i-1].Y - points[i].Y == 0)  slopes.Add(i, float.MaxValue);
        else slopes.Add(i, 
             1f * (points[i-1].X - points[i].X) / (points[i-1].Y - points[i].Y));
    }

    newPoints.Add(points[0]);
    for (int i = slopes.Count - 2; i > 0; i--)
    {
        if (Math.Abs(slopes[i] - slopes[i + 1]) < limit)
            toRemove.Add(i);   
    }

    foreach (int i in toRemove) slopes.Remove(i);

    newPoints.Add(points[points.Count-1]);
    foreach (KeyValuePair<int, float> kv in slopes) newPoints.Add(points[kv.Key]);

    return newPoints;
}

上面的图表是这样创建的:

private void button7_Click(object sender, EventArgs e)
{
    chart1.Series.Clear();        chart1.Series.Add("S1");
    chart1.Series.Add("S2");      chart1.Series.Add("S3");
    List<Point> points = new List<Point>();
    points.Add(new Point(1,2));   points.Add(new Point(2,5));
    points.Add(new Point(3,8));   points.Add(new Point(4,6));
    points.Add(new Point(5,4));   points.Add(new Point(6,2));
    points.Add(new Point(7,4));
    chart1.Series[0].ChartType = SeriesChartType.Line;
    chart1.Series[1].ChartType = SeriesChartType.Point;
    chart1.Series[2].ChartType = SeriesChartType.Point;
    chart1.Series[0].Points.Clear();
    foreach (Point pt in points)
    {
        chart1.Series[0].Points.AddXY(pt.X, pt.Y);
        chart1.Series[1].Points.AddXY(pt.X, pt.Y);
    }

    List<Point> reducedPoints = reducePlotLines(points);
    foreach (Point pt in reducedPoints)
    {
        chart1.Series[2].Points.AddXY(pt.X, pt.Y);
    }

}

请注意，我必须更改您的数据，因为它只包含一个插值点。