How do I use an if condition to tell whether two lines intersect?

I'm trying to use an if statement to plot a balls entire trajectory if it goes through a hole in the wall, and to plot the trajectory only up to the wall if it doesn't go through the hole. Is there a way to tell if the path of the ball intersects with the line of the wall?

Is there a way to see if this plot:

BallPositionX=function of t
BallPositionY=function of t
plot(BallPositionX,BallPositionY)

intersects with a vertical line (the wall)?

I've tried so many things, maybe I am overthinking it? Any help is much appreciated!

[KSSV]

You add the data you have....It can be calculated...

[Mandar Patwardhan]

Refer to the following MathWorks blog link which talks in detail about various ways to check if the two lines are intersecting each other.

http://blogs.mathworks.com/loren/2011/08/29/intersecting-lines/

You can write a function using the algorithms discussed in the blog and check the output of this function in an if condition.

Answer 1

[Image Analyst]

I assume you're looking at this only in 2-D so you have only x and y. You need to know the bottom y coordinate of the hole, and the top y coordinate of the hole. And you said you have (BallPositionX, BallPositionY) as a function of t. You must also know the radius of the ball so you know if it can fit through the hole or not, and you must know the x position of the wall, xWall. With all that you can do:

% Find index where the ball is at or to the right of the wall,
% assuming the ball is moving from left to right.
index = find(BallPositionX > xWall, 1, 'first');
% Find the y position of the center of the ball at that time.
yBallAtWall = BallPositionY(index);
% See if yBallAtWall is within the hole
if (yBallAtWall - ballRadius) > yHoleBottom && (yBallAtWall + ballRadius) < yHoleTop
    % It went through the hole.
else
    % It hit the wall.
end