public static void TestInterpolation2()
{
double[] x = new double[] { 0, 1 };
double[] y = new double[] { 0, 1 };
ACQ.Math.Interpolation.InterpolationInterface interpolator = new ACQ.Math.Interpolation.LinearInterpolation(x, y);
double xi = 0.5;
double yi = interpolator.Eval(xi);
}
/// <summary>
/// Construct Lowess
/// </summary>
/// <param name="x"></param>
/// <param name="y"></param>
/// <param name="nsteps"> number of robustifying iterations which should be performed. (default = 3) </param>
/// <param name="span">smoother span [0, 1], default = 2/3. This gives the proportion of points in the plot which influence the smooth at each value. Larger values give more smoothness</param>
/// <param name="delta">Defaults to 1/100th of the range of x</param>
public Lowess(double[] x, double[] y, double span = 2.0 / 3.0, int nsteps = 3, double delta = 0.0)
{
if (x == null || y == null)
{
throw new ArgumentNullException("Lowess input arrays can not be null");
}
if (x.Length != y.Length)
{
throw new ArgumentException("Lowess input arrays x and y should have the same length");
}
if (x.Length < 2)
{
throw new ArgumentException("Lowess input arrays should have at least 2 nodes");
}
if (nsteps < 0)
{
throw new ArgumentException("Lowess nsteps must be >= 0");
}
//the code below actually will work for any value of span (because it checks later), but R checks for negative span, so we as well for consistency
if (span < 0)
{
throw new ArgumentException("Lowess span must be > 0");
}
int n = x.Length;
//check that x is sorted
bool ordered = true;
for (int i = 0; i < n - 1; i++)
{
if (x[i + 1] < x[i]) //same values are allowed
{
ordered = false;
break;
}
}
double[] x_in = x;
double[] y_in = y;
if (!ordered)
{
//make copy and sort if provided array is not ordered
x_in = (double[])x.Clone();
y_in = (double[])y.Clone();
Array.Sort <double, double>(x_in, y_in);
}
if (delta <= 0.0)
{
delta = 0.01 * (x_in[n - 1] - x_in[0]); //same default as in R
}
double[] ys = new double[n];
clowess(x_in, y_in, ys, span, nsteps, delta); //this is main r - function
//check that all values of x_in are uniques
bool unique = true;
for (int i = 0; i < n - 1; i++)
{
if (x[i + 1] == x[i]) //same values are allowed
{
unique = false;
break;
}
}
if (unique)
{
m_interpolator = new ACQ.Math.Interpolation.LinearInterpolation(x_in, ys);
}
else
{
List <double> xu = new List <double>(n);
List <double> yu = new List <double>(n);
xu.Add(x_in[0]);
yu.Add(ys[0]);
double prev_x = x_in[0];
for (int i = 1; i < n; i++)
{
if (x_in[i] > prev_x)
{
xu.Add(x_in[i]);
yu.Add(ys[i]);
prev_x = x_in[i];
}
}
m_interpolator = new ACQ.Math.Interpolation.LinearInterpolation(xu.ToArray(), yu.ToArray());
}
}
