namespace IStation.Curve
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{
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/// <summary>
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/// 样条曲线（四次拟合）：使用MATH.net
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/// </summary>
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public class TwinRelateCurve4M : IFitPoint
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{
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/// <summary>
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///
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/// </summary>
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public TwinRelateCurve4M(CurveExpress express)
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{
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_express = express;
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}
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/// <summary>
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///
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/// </summary>
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public TwinRelateCurve4M(List<CurvePoint> points)
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{
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if (points == null || points.Count < 5)
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{
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throw new Exception("出现数值计算问题 ，无法解出四次样条曲线!");
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}
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_express = BuildCurveExpress(points);
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}
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//曲线表达式
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private CurveExpress _express = null;
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/// <summary>
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/// 获取拟合点Y
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/// </summary>
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public double GetFitPointY(double x)
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{
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if (_express == null)
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return default;
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//不用减掉最小值, 和alglib有点不一样
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return _express.Index4 * x * x * x * x + _express.Index3 * x * x * x + _express.Index2 * x * x + _express.Index1 * x + _express.Index0;
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}
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/// <summary>
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/// 获取拟合点列表
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/// </summary>
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public List<CurvePoint> GetFitPoints(int pointNumber)
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{
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if (_express == null)
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return default;
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return GetFitPointsByXRange(_express.Min, _express.Max, pointNumber);
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}
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/// <summary>
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/// 通过区间获取拟合点列表
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/// </summary>
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public List<CurvePoint> GetFitPointsByXRange(double minX, double maxX, int pointNumber)
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{
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if (_express == null)
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return default;
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if (pointNumber < 1)
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pointNumber = 12;
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if (pointNumber > 10000)
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pointNumber = 10000;
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double space = (maxX - minX) / (pointNumber - 1);
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if (space < 0.0001)
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return default;
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var points = new List<CurvePoint>();
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for (int i = 0; i < pointNumber; i++)
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{
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double x = space * i + minX;
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double y = this.GetFitPointY(x);
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points.Add(new CurvePoint(x, y));
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}
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return points;
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}
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/// <summary>
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/// 创建曲线表达式
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/// </summary>
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public static CurveExpress BuildCurveExpress(List<CurvePoint> points)
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{
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if (points == null || points.Count < 5)
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return default;
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points = points.OrderBy(x => x.X).ToList();
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CurveExpress express = new CurveExpress();
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express.FitType = eFitType.FourM;
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express.DefinePoints = points.Select(x => new CurvePoint(x)).ToList();
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express.Min = points.First().X;
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express.Max = points.Last().X;
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var X = (from x in points select x.X).ToArray();
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var Y = (from x in points select x.Y).ToArray();
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var res = MathNet.Numerics.Fit.Polynomial(X, Y, 4);
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//0次方
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express.Index0 = res[0];
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//1次方
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express.Index1 = res[1];
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//2次方
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express.Index2 = res[2];
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//3次方
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express.Index3 = res[3];
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//4次方
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express.Index4 = res[4];
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return express;
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}
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}
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}
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