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c#chartsmschart

Polar Plot with mschart C#

I'm currently working on a project, in which I need to create a Polar Plot with dynamically generated data. I've managed to create a somewhat decent polar plot, but have not been able to create what is needed. This is my Polar Plot

this is the code I used to set the offset in the middle:

    public Form1()
    {
        InitializeComponent();
        chart1.ChartAreas[0].AxisX.MajorTickMark.Enabled = false;
        chart1.ChartAreas[0].AxisX.MajorGrid.Enabled = false;


        chart1.ChartAreas[0].AxisY.Minimum = -20;
        chart1.ChartAreas[0].AxisY.MajorGrid.IntervalOffset = 15;
        chart1.ChartAreas[0].AxisY.MajorGrid.Interval = 5;
        chart1.ChartAreas[0].AxisY.MajorGrid.LineDashStyle = ChartDashStyle.Solid;
        chart1.ChartAreas[0].AxisX.MajorGrid.LineDashStyle = ChartDashStyle.Solid;

    }

I found some help here: How to displace the origin of the Y axis on a polar Mschart?

I got a example on how I'm trying to get the polar: The finished example

Solution

  • I don't think you can make an axis start from anywhere but its minimum.

    (The linked post only makes the labels start from a different value.)

    So we'll have to help with a little bit of owner-drawing.

    A few short references:

    var ca = chart1.ChartAreas[0];
var ax = ca.AxisX;
var ay = ca.AxisY;

    Now let's hide the y-axis:

    ay.LineWidth = 0;

    To draw the portion of the axis from the interval offset to the maximum we simply code the PostPaint event:

    private void chart1_PostPaint(object sender, ChartPaintEventArgs e)
{
    // add references..
    ..
    // then use values to calulate pixel coordinates..
    int py1 = (int)ay.ValueToPixelPosition(ay.Minimum + ay.IntervalOffset);
    int py2 = (int)ay.ValueToPixelPosition(ay.Maximum);
    int px  = (int)ax.ValueToPixelPosition(ax.Maximum -  ax.Minimum);

    // blue to make it stand out
    e.ChartGraphics.Graphics.DrawLine(Pens.Blue, px, py1, px, py2);
}

    Result:

    enter image description here

    Of course finding the right values for Interval, IntervalOffset, Minimum and Maximum is all up to you..

    Update: If you want to have a full set of shortened x-axis gridlines you could do a lot of math or use a graphics transform. As usual the latter is so much easier..:

    Graphics g = e.ChartGraphics.Graphics;
int pyc = (int)ay.ValueToPixelPosition(ay.Minimum);  // y-center
for (int i = 0; i < 360 / ax.Interval; i++)
{
    g.TranslateTransform(px, pyc);
    g.RotateTransform((float)(i * ax.Interval));
    g.TranslateTransform(-px, -pyc);
    g.DrawLine(Pens.colorOfYourChoice, px, py1, px, py2);
    g.ResetTransform();
}

    After setting ax.Interval = 30; we get this result:

    enter image description here