ColorLine and FastLine

[TomAgos]

im adding to the chart a FastLine with some random points.
this fastLine have custom y axis.
then im adding vertical ColorLine and allow drag.

assuming the ColorLine is touching the FastLine, i want to check what is the y value of this intersection point.
what is the best way to do that?

Thanks

[Edu]

Hello TomAgos,


We have a demo of ours that you can check on our github that explains this in more detail, Line_Interpolate to be precise.

Basically, through a function that looks like this

Code: Select all

        private double InterpolateLineSeries(Series series, int firstindex, int lastindex, double xvalue)
        {
            int index;
            for (index = firstindex; index <= lastindex; index++)
            {
                if (index == -1 || series.XValues.Value[index] > xvalue) break;
            }
            // safeguard
            if (index < 1) index = 1;
            else if (index >= series.Count) index = series.Count - 1;
            // y=(y2-y1)/(x2-x1)*(x-x1)+y1
            double dx = series.XValues[index] - series.XValues[index - 1];
            double dy = series.YValues[index] - series.YValues[index - 1];
            if (dx != 0.0) return dy * (xvalue - series.XValues[index - 1]) / dx + series.YValues[index - 1];
            else return 0.0;
        }

and call it using the colorLine.Value as "xvalue", like so:

Code: Select all

        private void TChart1_AfterDraw(object sender, Steema.TeeChart.Drawing.IGraphics3D g)
        {
            // I'm using a try catch block to suggest an idea or approach, use as desired
            try
            {       
                double value = InterpolateLineSeries(fastLine, fastLine.FirstVisibleIndex, fastLine.LastVisibleIndex, colorLine.Value);
                labelDisplay.Text = value.ToString();
            }
            catch(Exception e)
            {
           	 // Will only trigger if you remove the safety from InterpolateLineSeries() function
                labelDisplay.Text = "ColorLine not in range of FastLine"; 

            }
        }

The way to implement this code is definitely up to you. For example, if you only have one colorLine and one series that you want to check if it intersects or where, you can adjust the header of the function, removing "Series" and "xvalue" as parameters etc.

Finally, this is an example of how it would look like, using a label on the right of the chart to show the value:

ColorLineIntersection.png (27.71 KiB) Viewed 2519 times

Hope this helps, if there's anything else that I can help you with, please let me know!

Best regards,
Edu