Distance between two points - use ginput!

Hi quys, please do you have any idea, how two measure distance between two points? I have my script (below) and a need measure distance between two points. Its mean - when I click (use ginput) six-times - i have six points and I need measure distance between - first+second , third+fourth and fifth+sixth. Its mean I have six points and 3 distances. I need keep my script, I just wanna edit it. Do you have please any idea how to edit it?? Thanks everybody for help!!!

MY SCRIPT:

close all
axis ([0 100 0 100]);
hold on
xy = []; 
n = 0; 
distance = [];
disp('SELECT POINTS LEFT BUTTON')
disp('RIGHT-CLICK SELECTED LAST POINT')

but = 1;
while but == 1
    [xi,yi,but] = ginput(1);
    plot(xi,yi,'ro')
    n = n+1;
    xy(:,n) = [xi;yi];

end

Answer 1

[Thomas]

to find the distance between the two point use

http://en.wikipedia.org/wiki/Distance

d(1)= sqrt((x_point2-x_point1)^2+(y_point2-y_point1)^2);
d(2)= sqrt((x_point4-x_point3)^2+(y_point4-y_point3)^2);
d(3)= sqrt((x_point6-x_point5)^2+(y_point6-y_point5)^2);

you can generalize this and run it in a for loop

    d(i)=sqrt((x_point(2*i)-x_point(2*i-1))^2+(y_point(2*i)-y_point(2*i-1))^2);

This is not the exact code but, you should be able to code it according to your requirements.

In you example

     x_point1=xy(1,1)
     y_point1=xy(2,1)

and so on..

[Peter]

Thank you very much Thomas!!

Answer 2

[Matt Tearle]

Just because I can, here's a one-line version:

d = sqrt(sum([diff(reshape(xy(1,:),2,[]));diff(reshape(xy(2,:),2,[]))].^2))

In case you care, what this does is takes each x coordinate separately and reshapes them:

[x1 x2 x3 x4 ...]

to

[x1 x3 ...]
[x2 x4 ...]

Then takes the difference down the columns:

[x2-x1 x4-x3 ...]

Then the same with y, resulting in a matrix

[x2-x1 x4-x3 ...]
[y2-y1 y4-y3 ...]

Then squares, sums the columns, and takes the square root:

[sqrt((x2-x1)^2+(y2-y1)^2)  sqrt((x4-x3)^2+(y4-y3)^2) ...]