Function not recognising output

i am trying to make a user defined function for a unit converter in app designer. i have set up my code but when i run it the output ('num') says it is not recognised even though i have stated it is the output in the first line, do i need to do something else to this variable that i am missing? this is my code

function num = convert_func(x,conversion)

if conversion == 1

num = x/0.4536;

elseif conversion ==2

num = x*0.4536;

end

i also get this error message in app designer

Output argument "num" (and maybe others) not assigned during call to "convert_func"

Answer 1

[Walter Roberson]

conversion is something other than 1 or 2, or else it is non-scalar and has both values