public IEnumerable<double> CreatePoints(IPlotFunction function)
{
if (function == null)
{
throw new ArgumentNullException();
}
List<double> points = new List<double>(FunctionPlotSegment.CreatePoints(a, b, n));
List<double> values = new List<double>();
foreach (double x in points)
{
values.Add(function.Value(x));
}
List<double> points2 = new List<double>();
// Always keep the left-most point.
points2.Add(a);
//yield return a;
int i0 = 0;
while (i0 < n - 1)
{
// Find the largest span of points such that deviations in the y-direction between the linear interpolation
// and the true function values of intermediate points are no more than the tolerance.
// Currently using this left end-point.
double xl = points[i0];
double yl = values[i0];
// Perform at least one step.
int i = i0 + 1;
while (i < n - 1)
{
// Test with this right end-point one more step ahead.
double xr = points[i + 1];
double yr = values[i + 1];
// And then recheck all points in the range between these points.
bool stop = false;
for (int j = i0 + 1; j < i + 1; j++)
{
double x = points[j];
// The true value.
double y0 = values[j];
// The interpolated value.
double lambda = (xr - x) / (xr - xl);
double y = (1.0 - lambda) * yr + lambda * yl;
if (Math.Abs(y - y0) > tolerance || double.IsNaN(y) || double.IsNaN(y0))
{
// Deviation too large. Stop the expansion of the range.
stop = true;
break;
}
}
if (stop)
{
break;
}
// We've confirmed that the range can be expanded by one more point.
i++;
}
points2.Add(points[i]);
//yield return points[i];
// Use this point as the next left end-point.
i0 = i;
}
return points2;
}
public static PlotFunction Create(IPlotFunction f)
{
return Create(x => f.Value(x));
}
