MATLAB: Does anyone know why the 2nd conditional statement is being ignored in this while loop

conditional statementMATLAB

Does anyone know why my second conditional statement "units(1) ~= 'n'" is being ignored when this code block is run? When the 2nd statement is removed the code runs without problems.
   units = strings([1,4]);
   torque_force_input = input('Input the unit of force for your initial torque\n','s');
   units(1)= torque_force_input;
    
   while units(1) ~= 'N'||units(1) ~= 'n'
        disp('Please input a valid unit for the torque''s force.');
        torque_force_input = input('Input a unit of force for your torque...\n','s');
        units(1)= torque_force_input;
       
    end

Best Answer

Suppose i enter Nm in command window then units will be
units
units = 
  1×4 string array
    "Nm"    ""    ""    ""
if you try the access the first letter
units(1)
ans = 
    "Nm"
you have the complete word the user enters and not a single character
to access first index
units{1}(1)
ans =
    'N'
Now for the while loop, it keeps runing untill it receives false. so if user inputs N, so 
    'N' ~= 'N' || 'N' ~= 'n'
this will give you true and while loop will keep runing. you need a condition such that if any of them is true you get false and if both are false you get true
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