namespace IStation.Curve
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{
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/// <summary>
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/// 样条曲线（二次拟合）B=0
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/// </summary>
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public class TwinRelateCurve2B0 : IFitPoint
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{
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/// <summary>
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///
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/// </summary>
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public TwinRelateCurve2B0(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 TwinRelateCurve2B0(List<CurvePoint> points)
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{
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if (points == null || points.Count < 3)
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{
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throw new Exception("出现数值计算问题, 无法解出二次拟合曲线(B=0)！");
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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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{
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return default;
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}
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return _express.Index2 * x * 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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{
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return default;
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}
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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X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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{
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return default;
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}
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if (pointNumber < 1)
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{
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pointNumber = 12;
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}
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if (pointNumber > 10000)
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{
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pointNumber = 10000;
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}
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double space = (maxX - minX) / (pointNumber - 1);
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if (space < 0.0001)
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{
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return default;
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}
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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 = 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 < 3)
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{
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return default;
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}
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points = points.OrderBy(x => x.X).ToList();
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var count = points.Count;
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var express = new CurveExpress
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{
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FitType = eFitType.ConicCurveB0,
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DefinePoints = points.Select(x => new CurvePoint(x)).ToList(),
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Min = points.First().X,
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Max = points.Last().X
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};
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double rTotalH = 0.0;
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double rTotalHQ2 = 0.0;
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double rTotalQ2 = 0.0;
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double rTotalQ4 = 0.0;
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for (int i = 0; i < count; i++)
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{
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rTotalH = rTotalH + points[i].Y;
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rTotalHQ2 = rTotalHQ2 + points[i].Y * points[i].X * points[i].X;
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rTotalQ2 = rTotalQ2 + points[i].X * points[i].X;
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rTotalQ4 = rTotalQ4 + Math.Pow(points[i].X, 4);
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}
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express.Index2 = (rTotalH * rTotalQ2 - count * rTotalHQ2) / ((rTotalQ2 * rTotalQ2) - count * rTotalQ4);
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express.Index0 = (rTotalQ2 * rTotalHQ2 - rTotalQ4 * rTotalH) / ((rTotalQ2 * rTotalQ2) - count * rTotalQ4);
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return express;
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}
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}
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}
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