Mike - if you are requesting that the user enter a string, then you need to include the 's' option so that the input is not evaluated and is treated as a string. If you run your code as is, you are probably observing the
Error using input
Undefined function or variable 'st'.
when you type in st. Instead change the input call to
select_material=input('Choose a plate material,Steel (st),Aluminium Alloy (al): ','s');
Now, select_material will be a character array (or string) and you can compare the selection to the strings st and al. In your code, you are doing this as
if select_material==st
But since st is undefined and select_material is a string then this evaluation will fail. Instead use strcmpi to compare strings
if strcmpi(select_material,'st')
% do stuff
elseif strcmpi(select_material,'al')
% do other stuff
else
fprintf('invalid material %s\n',select_material);
end
Try the above and see what happens!
