问题描述：求点到直线的垂直距离

% 求点d1到直线d2-d3的距离。

function [d,dl] = VerticalDis(d1,d2,d3)

x1 = d1(1,1); y1 = d1(1,2);

x2 = d2(1,1); y2 = d2(1,2);

x3 = d3(1,1); y3 = d3(1,2);

if x2 == x3

x4 = x1 – 1;

y4 = y1;

elseif y2 == y3;

x4 = x1;

y4 = y1 – 1;

else

k23 = (y3-y2)/(x3-x2);

k1 = -1/k23;

x4 = x1 + 1;

y4 = k1*x4 + y1 – k1*x1;

end

d4 = [x4,y4];

[xx,yy] = node_solve(d1,d4,d2,d3);

dl = [xx,yy];

d = norm(dl-d1);

end

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

if X1(1) == Y1(1)

X = X1(1);

k2 = (Y2(2)-X2(2))/(Y2(1)-X2(1));

b2 = X2(2)-k2*X2(1);

Y = k2*X+b2;

end

if X2(1) == Y2(1)

X = X2(1);

k1 = (Y1(2)-X1(2))/(Y1(1)-X1(1));

b1 = X1(2)-k1*X1(1);

Y = k1*X+b1;

end

if X1(1) ~= Y1(1) & X2(1) ~= Y2(1)

k1 = (Y1(2)-X1(2))/(Y1(1)-X1(1));

k2 = (Y2(2)-X2(2))/(Y2(1)-X2(1));

b1 = X1(2)-k1*X1(1);

b2 = X2(2)-k2*X2(1);

if k1 == k2

X = [];

Y = [];

else

X = (b2-b1)/(k1-k2);

Y = k1*X+b1;

end

end

end