用matlab做橢圓擬合方程

1、具體不做說明，留著以后查找方便。clearclcload ('S.txt');r=S(:,1);t=S(:,2);x=r.*cos(t*pi/180);%轉(zhuǎn)換成直角坐標(biāo)y=r.*sin(t*pi/180);%轉(zhuǎn)換成直角坐標(biāo)XY=x,y;save X44.txt XY -ascii保存轉(zhuǎn)換后的直角坐標(biāo)%曲線方程擬合 %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橢圓一般方程 p0=1 1 1 1 11;%擬合系數(shù)，最小二乘法%p=nli

2、nfit(X Y zeros6ize(XY1),1), F, p0);%調(diào)整畫圖輸出樣式及大小s=4800/127;%轉(zhuǎn)換像素figure('position',200 200 16*s 16*s);%確定繪圖尺寸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('隧道斷面曲線擬合');legend(監(jiān)測點:擬合曲線');grid onP=P./P(6)；xc=(p(2)*p(5)-2*p(3)*p(4)/(4*p(1)*p(4)-p( 2)A2);%求橢圓中心坐標(biāo)yc=(p(2)*p(4)-2*p(1)*p( 5)/(4*p(1)*p(4)-p(2)A2);% 求橢圓中心坐標(biāo)angle=(1/2

4、)*atan(p(2)*(p(1)-p( 3)%求橢圓傾斜角度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)% 求橢圓長軸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)% 求橢圓短軸u=(a-b)/a%計算橢圓扁率%將扁率小數(shù)換算成千分?jǐn)?shù)%m=size(u);B=;B=u*1000;for i=1:mB=num2str(B(i),%'B=B 13

5、;%13為回車鍵的ASCI碼end%繪圖加注 %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')%為圖中每個點加注坐標(biāo)%for j=1:length(x)str=strcat('(',num2str(x(j),',',num2str(y(j),')');text(x(j