Question

怎么用matlab拟合出椭圆方程

知道一组x，y的坐标，比如x=1132，y =574；x=350,y=419;x=222,y=828;x=334,y=1024;x=890,y=1034；
x=1036,y=856;x=1064,y=586;x=880,y=337;怎么拟合出椭圆的方程

Answer 1

首先要下一个拟合工具 （在附件中），解压安装

x=[1132,350,222,334,890,1036,1064,880];

y =[574,419,828,1024,1034,856,586,337];

XY=[x;y]';

A = EllipseDirectFit(XY);

% A = [a b c d e f]

%  ax^2 + bxy + cy^2 + dx + ey + f = 0

hold on

%Convert the A to str 

a = num2str(A(1)); 

b = num2str(A(2)); 

c = num2str(A(3)); 

d = num2str(A(4)); 

e = num2str(A(5)); 

f = num2str(A(6));

%Equation 

eqt= ['(',a, ')*x^2 + (',b,')*x*y + (',c,')*y^2 + (',d,')*x+ (',e,')*y + (',f,')']; 

xmin=0.7*min(XY(:,1)); 

xmax=1.3*max(XY(:,2)); 

ezplot(eqt,[xmin,xmax]) 

scatter(XY(:,1),XY(:,2),'r') 

hold off