如何在 C# 中的图表上放置以对数表示的行的对数刻度 [英] How to put a logarithmic scale with rows represented in logarithm on chart in C #

问题描述

我正在用 C# 开发一个图表，我需要用对数表示图形线，比例已经可以放置，只是根据下图缺少对数比例中的垂直线:

I'm developing a chart in C # and I need the graph lines to be represented in logarithm, the scale can already put, just missing the vertical lines in logarithmic scale according to the image below:

我的图表目前如下所示:

My chart currently looks like this:

推荐答案

更新:

要在您需要为图表区域的 x 轴打开 MinorGrid 的时间段之间获得这些额外的线:

To get those additional lines between the periods you need to turn on the MinorGrid for the x-axis of your chartArea:

chart.ChartAreas[0].AxisX.MinorGrid.Enabled = true;
chart.ChartAreas[0].AxisX.MinorGrid.Interval = 1;

这显然比自己绘制它们容易得多，因为我认为这是必要的..

This is obviosly a lot easier than drawing them yourself, as I thought was necessary..

不过，我将自己绘制的解决方案留在下面，因为它在做一些特殊的事情时可能很有用，比如使用不寻常的笔或自定义间隔..

I leave the owner-drawn solution below, though, as it may be useful when doing extra special stuff, like using unsusual pens or customizing the intervals..

(我很高兴看到结果是一样的 :-)

(And I was glad to see that the results are identical :-)

使用所有者绘制的 GridLine 的旧解决方案:

以下是如何所有者绘制对数轴的网格线.

Here is how you can owner-draw the gridlines for a logarithmic axis.

为了定义区间规则，我首先收集一个双值列表作为停止值.沿 x 轴.

To define the interval rules I first collect a List of double values for the stop values. along the x-axis.

这是一个在每个时期使用 10 条网格线的示例..

Here is an example using 10 gridlines in each period..

图表的 x 轴设置为 Minimum = 0.1d 和 Maximum = 1000.

The chart's x-axis was set up with Minimum = 0.1d and Maximum = 1000.

private void chart_PrePaint(object sender, ChartPaintEventArgs e)
{
    ChartArea ca = chart.ChartAreas[0];
    Graphics g = e.ChartGraphics.Graphics;
    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;

    // first get y top and bottom values:
    int y0 = (int)ca.AxisY.ValueToPixelPosition(ca.AxisY.Minimum);
    int y1 = (int)ca.AxisY.ValueToPixelPosition(ca.AxisY.Maximum);

    int iCount = 10;                         // number of gridlines per period
    var xes = new List<double>();            // the grid position values
    double xx = ca.AxisX.Minimum;
    do {
       xx *= ca.AxisX.LogarithmBase;         // next period
       double delta = 1d * xx / iCount ;     // distance in this period
       for (int i = 1; i < icount; i++) xes.Add(i * delta);  // collect the values
    }  while (xx < ca.AxisX.Maximum);

    // now we can draw..
    using (Pen pen = new Pen(Color.FromArgb(64, Color.Blue))
          {DashStyle = System.Drawing.Drawing2D.DashStyle.Dot} )
       foreach (var xv in xes)
       {
           float x = (float)ca.AxisX.ValueToPixelPosition(xv);
           g.DrawLine(pen, x, y0, x, y1);
       }
}

您可以缓存 x 值列表，但必须在数据或轴视图更改时重新计算..

You could cache the x-values list but would have to re-calculate whenever the data or the axis view changes..

请注意，在收集网格停止值时，我们从 1 开始计数，因为我们不想将一个周期的起点加倍:1..9 + 10..90 等.所以我们实际上只添加了 count-1 个网格停止点..

Note that, when collection the grid stop values, we count from 1 because we don't want to double the starting points of a period: 1..9 + 10..90 etc. So we actually add only count-1 grid stops..

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