www.pudn.com > spline_c++.rar > spline.cpp

#include "spline.h" 
 
void GetDerivdowntive2(double down[] ,   //对三角矩阵的下半部分  
					double upper[],    //对三角矩阵的上半部分  
					PointInfo *pInfo,    //方程右边的常数部分，同时作为导数的输出存放区  
					int n)        //矩阵的维数  
{ 
	upper[1]/=2; 
	for (int i =2 ; iyDer2/= 2; 
	for (int i =2; i<=n; i++){ 
		(pInfo+i)->yDer2=((pInfo+i)->yDer2-down[i]*((pInfo+i-1)->yDer2))/ 
			(2-down[i]*upper[i-1]);   
	}  
	for (int i=n-1; i>0; --i){ 
		((pInfo+i)->yDer2)-=upper[i]*(pInfo+i+1)->yDer2; 
	} 
	pInfo->yDer2=(pInfo+n+1)->yDer2=0; 
}  
 
void GenarateArray(PointInfo *pBegin,int newLengh, char *pDes, int oldLengh) 
{ 
	int nDesPos = 0; 
	PointInfo *pLeft,*pRight; 
	while(nDesPos < newLengh-1) 
	{ 
		if(nDesPos == pBegin->x) 
		{ 
			*(pDes+nDesPos) = (int)(pBegin->yDer2); 
			nDesPos++; 
			pBegin++; 
		} 
		else  
			if(nDesPos < pBegin->x) 
			{ 
				pRight = pBegin; 
				pLeft  = pBegin-1; 
				GenarateData(pLeft, pRight, pDes, nDesPos); 
				nDesPos ++; 
			} 
	} 
} 
 
void GenarateData(PointInfo *pLeft, PointInfo *pRight, char *pDes, int pos) 
{ 
	double h =   pRight->x - pLeft->x; 
	double xR =  pRight->x - pos;  
	double xL =	  pos -pLeft->x; 
	*(pDes+pos)= (char)((pLeft->yDer2)*pow( xR,3)/h/6 + 
 
		         (pRight->yDer2)*pow( xL ,3)/h+ 
 
				 (pLeft->y - (pLeft->yDer2)*pow(h, 2)/6)*xR/h+ 
 
				 (pRight->y - (pRight->yDer2)*pow(h, 2)/6)*xL/h); 
 
 
		          
} 
 
void GenarateMatrix(double upper[], double down[], PointInfo *pInfo , int oldLength) 
{ 
    
  
   for(int k=1; k< oldLength  ;k++) 
   { 
	   upper[k] = ((pInfo+k+1)->x -(pInfo+k)->x)/((pInfo+k+1)->x-(pInfo+k-1)->x); 
	   (pInfo+k)->yDer2 = (((pInfo+k+1)->y-(pInfo+k)->y)/((pInfo+k+1)->x -(pInfo+k)->x) - ((pInfo+k)->y - (pInfo+k-1)->y)/((pInfo+k)->x-(pInfo+k-1)->x))*6/ 
		          ((pInfo+k+1)->x-(pInfo+k-1)->x); 
	   if(k>1) 
		   down[k-1] = 1- upper[k]; 
 
   } 
} 
void GenaratePiontInfo(PointInfo *pInfo ,char *pSrc, int oldLength,int newLength) 
{ 
	 double scale; 
	  
	 scale = newLength /oldLength; 
	 for(int k = 0;k< oldLength ; k++) 
	 { 
		 (pInfo+k)->x = k*scale; 
		 (pInfo+k)->y = *(pSrc+k); 
 
	 } 
}