[求助]matlab求圆心坐标 - MATLAB爱好者论坛-LabFans.com

tangguoge · 2007-11-28, 22:15

已知模型为(x-a)^2+(y-b)^2=r^2，给出十组x,y
，怎么编程求a,b,r

fanxing39 · 2007-12-02, 21:39

function [xc,yc,R,a] = circfit(x,y)
%CIRCFIT Fits a circle in x,y plane
% [XC, YC, R, A] = CIRCFIT(X,Y)
% Result is center point (yc,xc) and radius R.A is an

% optional output describing the circle's equation:
% x^2+y^2+a(1)*x+a(2)*y+a(3)=0

n=length(x);
xx=x.*x;
yy=y.*y;
xy=x.*y;
A=[sum(x) sum(y) n;sum(xy) sum(yy) sum(y);sum(xx) sum(xy) sum(x)];
B=[-sum(xx+yy) ; -sum(xx.*y+yy.*y) ; -sum(xx.*x+xy.*y)];
a=A\B;
xc = -.5*a(1);
yc = -.5*a(2);
R = sqrt((a(1)^2+a(2)^2)/4-a(3));

2007-11-28, 22:15	#1
tangguoge 初级会员注册日期: 2007-11-28 帖子: 1 声望力: 0	[求助]matlab求圆心坐标已知模型为(x-a)^2+(y-b)^2=r^2，给出十组x,y ，怎么编程求a,b,r

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2007-12-02, 21:39	#2
fanxing39 高级会员注册日期: 2007-12-02 年龄: 44 帖子: 303 声望力: 31	function [xc,yc,R,a] = circfit(x,y) %CIRCFIT Fits a circle in x,y plane % [XC, YC, R, A] = CIRCFIT(X,Y) % Result is center point (yc,xc) and radius R.A is an % optional output describing the circle's equation: % x^2+y^2+a(1)x+a(2)y+a(3)=0 n=length(x); xx=x.x; yy=y.y; xy=x.y; A=[sum(x) sum(y) n;sum(xy) sum(yy) sum(y);sum(xx) sum(xy) sum(x)]; B=[-sum(xx+yy) ; -sum(xx.y+yy.y) ; -sum(xx.x+xy.y)]; a=A\B; xc = -.5a(1); yc = -.5*a(2); R = sqrt((a(1)^2+a(2)^2)/4-a(3));