insertvalue.cpp

数值计算中 插值算法的实现 及其图像图例

#include<GL/glut.h>
#include<math.h>
#include<iostream.h>

const maxN=32;
int  nValue=16;

typedef struct tagPoint
{
	float x;
	float y;
}Point;

void init()
{
	glClearColor(1.0,1.0,1.0,0.0);
	glMatrixMode(GL_PROJECTION);
	gluOrtho2D(-200.0,200.0,0.0,300.0);
}
void setPixel(float xCoord,float yCoord)
{
	glBegin(GL_POINTS);
	glVertex2i((int)200*xCoord,(int)200*yCoord);
	glEnd();
}

void paintFx()
{
	float x=-1.0;
	float y;
	glColor3f(0.0,0.0,0.0);
	for(int k=0;k<1000;k++)
	{
		y=1.0/(1+25*x*x);
		setPixel(x,y);
		x+=0.002;
	}
}

void insertValue(int n)//n等份点
{
	Point points[maxN+1];
	float diff[maxN+1];
	float x=-1.0;
	int i,j;
	for(i=0;i<=n;i++)
	{
		points[i].x=x;
		points[i].y=1.0/(1+25*x*x);
		x+=2.0/n;
	}
	for(i=0;i<=n;i++)
		diff[i]=points[i].y;
	for (i=0;i<n;i++)
		for(j=n;j>i;j--)
			diff[j]=(diff[j]-diff[j-1])/(points[j].x-points[j-1-i].x);
	glColor3f(1.0,0.0,0.0);
	x=-1.0;
	for(i=0;i<1000;i++)
	{
		float tmp=1.0,newton=diff[0];
		for(j=0;j<n;j++)
		{
			tmp=tmp*(x-points[j].x);
			newton+=tmp*diff[j+1];
		}
		setPixel(x,newton);
		x+=0.002;
	}
}

void paintAll()
{
	glClear(GL_COLOR_BUFFER_BIT);
	paintFx();//绘制f(x)
	insertValue(nValue);
	glFlush();
}
void main(int argc,char **argv)
{
	cout<<"输入n等分的n值："<<endl;
	cin>>nValue;
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
	glutInitWindowPosition(50,100);
	glutInitWindowSize(400,300);
	glutCreateWindow("Computing Method Programme");

	init();
	glutDisplayFunc(paintAll);
	glutMainLoop();
}

/*
实验完成人：pb03011103  肖璟

  */