Why do I keep on getting wrong choice?

So just a little background info, I am trying to write a script that uses a menu and a switch so the user can choose to compute and report one of the following three pieces of information: The maximum height, the minimum velocity, or the time to hit. The equations I use for maximum height, minimum velocity, and time to hit are including in my code and they are for a projectile (such as a thrown ball) launched with an initial speed of V0 at an angle A to the horizontal (use input functions). My given is 9.80 m/s2 for the acceleration of gravity, g. I want to test my script for an initial velocity of 40 m/s and an angle of 30°. My code so far is this:

v0 = input('Enter the initial speed: ');%meters per second
A = input('Enter the angle: ');%degrees
g = 9.8;%meters per second squared
quantity = menu('Choose a quantity','height','velocity','time to hit');
A_rad = A*pi/180;
switch quantity
    case 'height'
        height = (v0^2*sin(A_rad))/(2*g);
    case 'velocity'
        velocity = v0*cos(A_rad);
    case 'time to hit'
        time_to_hit = 2*(v0/g)*sin(A_rad);
    otherwise
        disp('Wrong choice')
end

The problem is when I run my script, my menu pops up with the three options. But when I select any of the options(either height, velocity, or time to hit) I get this:

>> ThrownBall
Enter the initial speed: 40
Enter the angle: 30
Wrong choice

My menu is correct but somehow I keep getting 'Wrong choice', any pointers on how to fix my code so it can run correctly??

[Stephen23]

A tip to make the code a bit more robust: use the 's' option, and wrap input in str2double:

v0 = str2double(input('Enter the initial speed: ','s'));

This will correctly return any scalar numeric value, but if the user enters an invalid value (e.g. multiple values, or something that is not a number) it will simply return NaN.

Answer 1

[Birdman]

quantity returns either 1, 2 or 3. Therefore your code should look like this:

v0 = input('Enter the initial speed: ');%meters per second
A = input('Enter the angle: ');%degrees
g = 9.8;%meters per second squared
quantity = menu('Choose a quantity','height','velocity','time to hit');
A_rad = A*pi/180;
switch quantity
    case 1
        height = (v0^2*sin(A_rad))/(2*g);
    case 2
        velocity = v0*cos(A_rad);
    case 3
        time_to_hit = 2*(v0/g)*sin(A_rad);
    otherwise
        disp('Wrong choice')
end

1 for height, 2 for velocity and 3 for time to hit.

[T.Y. Hilton]

Gotcha I see what you are saying! Also I'm sorry if I'm being a pain in the butt, but when I changed it my code ran like this,

>> ThrownBall
Enter the initial speed: 40
Enter the angle: 30

It ran without giving me the answer ! I'm new to Matlab so I'm not quite sure how to fix this..maybe there is something wrong with my switch function?

[Birdman]

That is because every statement in case has a semicolon at the end, telling it to not display the answer. Do this:

v0 = input('Enter the initial speed: ');%meters per second
A = input('Enter the angle: ');%degrees
g = 9.8;%meters per second squared
quantity = menu('Choose a quantity','height','velocity','time to hit');
A_rad = A*pi/180;
switch quantity
    case 1
        height = (v0^2*sin(A_rad))/(2*g);
        disp(height)
    case 2
        velocity = v0*cos(A_rad);
        disp(velocity)
    case 3
        time_to_hit = 2*(v0/g)*sin(A_rad);
        disp(time_to_hit)
    otherwise
        disp('Wrong choice')
end

[T.Y. Hilton]

It worked! Thank you!