MATLAB: Break out of for loop help

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I have this for loop which works perfectly fine except that I want it to stop the for loop when y=0. The loop is calculating trajectory so I want it to stop when the ball hits the ground (or y=0). I have tried everything I can think of but nothing works. It either doesn't stop the loop or it returns the completely wrong y values. I've tried if y==0, y<=0, y(n)==0, y(n)<=0, y(n+1)==0, y(n+1)<=0, and putting it before and after the calculations. nothing worked Please help.
for n=1:N
    ax(n+1) = -D*vx(n)*v(n);
    ay(n+1) = -D*vy(n)*v(n)-g;
    v(n+1) = sqrt(vx(n)^2+vy(n)^2);
    x(n+1) = x(n)+T*vx(n)+0.5*T^2*ax(n);
    vx(n+1) = vx(n)+T*ax(n);
    y(n+1) = y(n)+T*vy(n)+0.5*T^2*ay(n);
    vy(n+1) = vy(n)+T*ay(n);
    if y(n+1)==0, break; end
end

Best Answer

The loop does stop. You can check this by a disp statement before the break.
I assume you have written the code into a script and y is defiend from an earlier run. Then a "clear" statement on top would be helpful - not "clear all". Or you could convert it to a function by inserting this as first line:
function myIntegrator
or what ever your file is called.
Note: Using several commands in one line impedes debugging. You cannot set a breakpoint on the break command in:
if y(n+1)==0, break; end
But this would have revealed the problem.
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