Problem with conditions in If statement

i am trying to fool proof my code. If i were to put 3 as the input for the varible, unit; it will loop back one but then skip a couple of commands.

Sorry, if my explainantion doesn't make sense :)

This screenchot is me just following the directions:

Now if I were to try and enter a number other than 1 or 2:

function [vf, k]=hhvelocity10
clc
close all
format compact
fprintf('\n')
unit=input(['Enter 1 to work with an initial velocity or enter 2 to work \n ' ...
    'with a pre-selected initial velocity = '],'s');
fprintf('\n')
initialvelocity='1';
preinitialvelocity='2';
if contains (unit,initialvelocity)
    g=9.8;
    InitialVelocity=input('Please give me the Initial Velocity in meters per second = ');
    fprintf('\n')
    InitialHeight=input('Please give me the Initial Height in meters = ');
    fprintf('\n')
    y=InitialHeight;
    v=InitialVelocity;
    vf=sqrt(2*g*y+v.^2);
    fprintf('The velocity is %.2f m/s \n', vf);
    fprintf('\n')
elseif contains (unit,preinitialvelocity)
    fprintf('Your pre-selected velocity is 10 m/s. \n')
    fprintf('\n')
    g=9.8;
    InitialHeight=input('Please give me the Initial Height in meters = ');
    fprintf('\n')
    y=InitialHeight;
    v=10;
    vf=sqrt(2*g*y+v.^2);
    fprintf('The velocity is %.2f m/s \n', vf);
    fprintf('\n')
else
    (unit~=1 || unit~=2);
    disp('Please enter 1 or 2.')
    unit=input(['Enter 1 to work with an initial velocity or enter 2 to work \n ' ...
        'with a pre-selected initial velocity = '],'s');
    fprintf('\n')
end
mu=input(['Please enter the coefficient of friction of the rough \n' ...
    'horizontal surface = ']);
fprintf('\n')
m=input('Please enter the mass of the object in kg = ');
fprintf('\n')
f=mu*m*g;
x=input(['Please enter the distance you want the object to travel on \n' ...
    'the rough horizontal region in meters = ']);
fprintf('\n')
x_s=input(['How far would you like for the object to compress \n' ...
    'the spring in meters? ']);
fprintf('\n')
v_f=vf;
v_i=v_f;
x_f=x_s;
k=(2*(-f)*(x+x_s))/(x_f.^2)+(m*v_i.^2)/(x_f.^2);

[Dyuman Joshi]

So if I am understanding it correctly, If someone enters a value other than 1/2, you want to ask them to enter again, either 1 or 2?

[Miya Harris]

Yes.

Answer 1

[Voss]

Typically you'd ask the user for input and check that the input is valid inside a while loop, because you need to keep asking until the given input is valid. Something like this:

unit = ''; % initialize to some invalid input value
while ~ismember(unit,{'1' '2'}) % iterate while unit is invalid
    unit=input(['Enter 1 to work with an initial velocity or enter 2 to work \n ' ...
        'with a pre-selected initial velocity = '],'s');
    fprintf('\n')
end