用matlab做椭圆拟合方程

1、具体不做说明，留着以后查找方便。clearclcload ('S.txt');r=S(:,1);t=S(:,2);x=r.*cos(t*pi/180);%转换成直角坐标y=r.*sin(t*pi/180);%转换成直角坐标XY=x,y;save X44.txt XY -ascii保存转换后的直角坐标%曲线方程拟合 %F=(p,XY)p(1)*XY(:,1)A2+p (2) *XY(:,1).*XY(:,2)+p (3)*XY(:,2).A2+p (4) *XY(:,1)+p(5)*XY(:,2)+p(6椭圆一般方程 p0=1 1 1 1 11;%拟合系数，最小二乘法%p=nli

2、nfit(X Y zeros6ize(XY1),1), F, p0);%调整画图输出样式及大小s=4800/127;%转换像素figure('position',200 200 16*s 16*s);%确定绘图尺寸axes('linewidth',3, 'box', 'on', 'FontSize',11,'FontName','Times New Roman');plot(XY(:,1), XY(:,2), 'ro'); hold on;xmin=min(XY(:,

3、 1); xmax=max(XY(:, 1);ymin=min(XY(:, 2); ymax=max(XY(:, 2);ezplot(x,y)F(p,x,y), -1+xmin,1+xmax,-1+ymin,1+ymax);title('隧道断面曲线拟合');legend(监测点:拟合曲线');grid onP=P./P(6)；xc=(p(2)*p(5)-2*p(3)*p(4)/(4*p(1)*p(4)-p( 2)A2);%求椭圆中心坐标yc=(p(2)*p(4)-2*p(1)*p( 5)/(4*p(1)*p(4)-p(2)A2);% 求椭圆中心坐标angle=(1/2

4、)*atan(p(2)*(p(1)-p( 3)%求椭圆倾斜角度a=sqrt(2*(p(1)*xcA2+p(3)*ycA2+ p(2)*xc*yc-1)/(p(1)+p(3)+(p(1)-p(3)A2+p(2)A2)A(1/2)% 求椭圆长轴b=sqrt(2*(p(1)*xcA2+p(3)*ycA2+p (2) *xc*yc- 1)/(p(1)+p(3)-(p(1)-p(3)A2+p (2) A2)A(1/2)% 求椭圆短轴u=(a-b)/a%计算椭圆扁率%将扁率小数换算成千分数%m=size(u);B=;B=u*1000;for i=1:mB=num2str(B(i),%'B=B 13

5、;%13为回车键的ASCI码end%绘图加注 %hold onplot(xc,yc,'ro')text(3.0,-2.8,'扁率=',num2str(B),'verticalAlignment','bottom','HorizontalAlignment','right','FontSiz e',12,'FontName','Times New Roman')%为图中每个点加注坐标%for j=1:length(x)str=strcat('(',num2str(x(j),',',num2str(y(j),')');text(x(j