Unrecognized function or variable 'x'. Error in circular (line 3) if x == 'C' Error in mainapp (line 7) circular;

Hi can someone help me with this code, it is a menu-driven code

THIS IS THE MAIN SCRIPT

choice = ectoption;
while choice ~= 4
    switch choice
        case 1
            explainapp;
        case 2
            circular;
        case 3
            triangular;
    end
end

THEN THIS IS THE SCRIPT CONNECTED TO IT
function circular
if x == 'C'
r = input("Enter the Radius: ");
disp("Circumference is ");
disp(2*pi*r);
  
elseif x == 'A'
disp("Area is ");
disp(pi*r*r);
elseif x == 'V'
disp("Volume is ");
disp(4*pi*r*r*r/3);
end
  
end

the error that keeps on popping out is 
Unrecognized function or variable 'x'.

Error in circular (line 3)
if x == 'C'

Error in mainapp (line 7)
            circular;
 

Answer 1

[Ben McMahon]

Your issue is that you have not told MATLAB what x is. Your function circular as it is written above has no idea what x, even if it is defined in another function or script as it does not exist in your functions workspace.

A simple solution is to pass x (if it exists elsewhere!) in as a argument to circular for example:

function circular(x)
     % your code here         
end

If for whatever reason you cannot pass function arguments, study the documentation for assigin.

As an aside, to diagnose errors such as this in the future, try using the debugger in MATLAB. For example you could place a breakpoint near the beginning of the function circular and you should see that x does not appear in the function workspace.