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76 lines
2.0 KiB
76 lines
2.0 KiB
/*
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* Work in this file is derived from code originally written by Hans-Peter Moser:
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* http://www.mosismath.com/AngleSplines/EndSlopeSplines.html
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*/
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namespace Connected.Components;
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public class EndSlopeSpline : SplineInterpolator
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{
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public EndSlopeSpline(double[] xs, double[] ys,
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int resolution = 10, double firstSlopeDegrees = 0, double lastSlopeDegrees = 0) :
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base(xs, ys, resolution)
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{
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m = new Matrix(n);
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gauss = new MatrixSolver(n, m);
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a = new double[n];
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b = new double[n];
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c = new double[n];
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d = new double[n];
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h = new double[n];
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CalcParameters(firstSlopeDegrees, lastSlopeDegrees);
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Integrate();
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Interpolate();
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}
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public void CalcParameters(double alpha, double beta)
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{
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for (int i = 0; i < n; i++)
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a[i] = GivenYs[i];
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for (int i = 0; i < n - 1; i++)
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h[i] = GivenXs[i + 1] - GivenXs[i];
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m.a[0, 0] = 2.0 * h[0];
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m.a[0, 1] = h[0];
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m.y[0] = 3 * ((a[1] - a[0]) / h[0] - Math.Tan(alpha * Math.PI / 180));
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for (int i = 0; i < n - 2; i++)
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{
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m.a[i + 1, i] = h[i];
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m.a[i + 1, i + 1] = 2.0 * (h[i] + h[i + 1]);
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if (i < n - 2)
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m.a[i + 1, i + 2] = h[i + 1];
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if ((h[i] != 0.0) && (h[i + 1] != 0.0))
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m.y[i + 1] = ((a[i + 2] - a[i + 1]) / h[i + 1] - (a[i + 1] - a[i]) / h[i]) * 3.0;
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else
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m.y[i + 1] = 0.0;
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}
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m.a[n - 1, n - 2] = h[n - 2];
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m.a[n - 1, n - 1] = 2.0 * h[n - 2];
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m.y[n - 1] = 3.0 * (Math.Tan(beta * Math.PI / 180) - (a[n - 1] - a[n - 2]) / h[n - 2]);
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if (gauss.Eliminate() == false)
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throw new InvalidOperationException();
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gauss.Solve();
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for (int i = 0; i < n; i++)
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{
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c[i] = m.x[i];
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}
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for (int i = 0; i < n; i++)
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{
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if (h[i] != 0.0)
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{
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d[i] = 1.0 / 3.0 / h[i] * (c[i + 1] - c[i]);
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b[i] = 1.0 / h[i] * (a[i + 1] - a[i]) - h[i] / 3.0 * (c[i + 1] + 2 * c[i]);
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}
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}
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}
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}
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