/// <summary>
/// Calculate y=y(x) for arbitrary x. Works fine only for line series with ordered x values.
/// </summary>
/// <param name="series"></param>
/// <param name="firstindex"></param>
/// <param name="lastindex"></param>
/// <param name="xvalue"></param>
/// <returns>y=y(xvalue) where xvalue is arbitrary x value.</returns>
private double InterpolateLineSeries(TeeChart.Styles.Custom 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);
}
}
private double InterpolateLineSeries(TeeChart.Styles.Custom series, double xvalue)
{
return(InterpolateLineSeries(series, series.FirstVisibleIndex, series.LastVisibleIndex, xvalue));
}
