转自《工程计算可视化与MA TLAB实现》尚涛等编著武汉大学出版社(1)两直线相交

function [X,Y]=pll(X1,Y1,X2,Y2)

% 直线相交求交点

A1=Y1(1)-Y1(2);

B1=X1(2)-X1(1);

C1=Y1(2)*X1(1)-Y1(1)*X1(2);

A2=Y2(1)-Y2(2);

B2=X2(2)-X2(1);

C2=Y2(2)*X2(1)-Y2(1)*X2(2);

D=det([A1,B1;A2,B2]);

X=det([-C1 B1;-C2 B2])/D;

Y=det([A1 -C1;A2,-C2])/D;

调用格式：

x1=[1 5];y1=[1 5];x2=[1 5];y2=[5,1];

[x,y]=pll(x1,y1,x2,y2);

plot(x1,y1,\'r\');

hold on

plot(x2,y2,\'b\');

plot(x,y,\'ko\');

(2)直线与多条直线相交

xi=[1 2 3 4 5];yi=[2 6 3 6 1];

plot(xi,yi);hold on

x1=[1 5];y1=[4 5];line(x1,y1);

x=zeros(size(xi));

y=x;

for i=1:5-1

x2=xi([i i+1]);y2=yi([i i+1]);

[x,y]=pll(x1,y1,x2,y2);

plot(x,y,\'ro\')

end