matlab编程求点的坐标

三点坐标（a,b）（c,d）（e,f）无序
定义函数
function [x2,y2] = fourth(x,y)

z = x+j*y;
r(1) = abs(z(1)-z(2));
r(2) = abs(z(2)-z(3));
r(3) = abs(z(1)-z(3));
rmax = max(r);
k = 0;
for i = 1:3
if r(i)==rmax
k = i;
end
end
switch k
case 1
z(4) = z(1)+z(2)-z(3);
case 2
z(4) = z(2)+z(3)-z(1);
case 3
z(4) = z(1)+z(3)-z(2);
end
x2 = [x, real(z(4))];
y2 = [y,imag(z(4))];

输入命令：
x = [a c e];y = [b d f];
[x,y] = fourth(x,y)
plot(x,y,'o')

%新坐标在x(4),y(4)