拉格朗日插值拟合

pre define

typedef struct Operators
{
	std::vector Operatos;

}Operators;

// 定义一个点
class PointF
{
public:
	PointF()
	{
		X = Y = 0.0f;
	}

	PointF(IN const PointF &point)
	{
		X = point.X;
		Y = point.Y;
	}

	PointF(IN float x,
		IN float y)
	{
		X = x;
		Y = y;
	}

	PointF operator+(IN const PointF& point) const
	{
		return PointF(X + point.X,
			Y + point.Y);
	}

	PointF operator-(IN const PointF& point) const
	{
		return PointF(X - point.X,
			Y - point.Y);
	}

	BOOL Equals(IN const PointF& point)
	{
		return (X == point.X) && (Y == point.Y);
	}

public:

	float X;
	float Y;
};

fit lagrange

void CWinaTVWaveformDlg::fitLagrange(std::vector pointList)
{
	std::vector  OpList;

	// result 
	std::vector Xs;
	std::vector Ys;

	try
	{
		if (pointList.size() > 0)
		{
			//compute lagrange operator for each X coordinate
			for (int x = 1; x < 2000; x++)
			{
				//list of float to hold the Lagrange operators, Init the list with 1's
				std::vector L(pointList.size(), 1);  

				for (int i = 0; i < L.size(); i++)
				{
					for (int k = 0; k < pointList.size(); k++)
					{
						if (i != k)
							L[i] *= (float)(x - pointList[k].X) / (pointList[i].X - pointList[k].X);
					}
				}
				Operators o;
				o.Operatos = L;
				OpList.push_back(o);
				Xs.push_back(x);

			}

			//Computing the Polynomial P(x) which is y in our curve
			std::vector::iterator iter;
			for ( iter = OpList.begin(); iter != OpList.end(); iter++)
			{
					float y = 0;
					for (int i = 0; i < pointList.size(); i++)
					{
						y += iter->Operatos[i] * pointList[i].Y;
					}

					Ys.push_back(y);
				   
			}

			//Drawing the curve in the simplest way

		}
		else
		{
			AfxMessageBox(_T("Lagrange curve fitting, add some points"));
		}
	}
	catch (CException* e)
	{
		return;
	}
}