How to limit user input to only one character?

I'm trying to figure out a way to limit user input to only one character and makes sure that its a letter. I figured out that to make sure that it is a capital letter I can use if all(ismember(variablename,65:90)), but I dont know how to make matlab only accept one character as a user input. Thanks, in advance, for the help.

Answer 1

[Image Analyst]

Try casting to upper and taking only the first character

variablename = upper(variablename); % Cast to upper case.
variablename = variablename(1); % Extract first character only.
if ~isletter(variablename)
    message = sprintf('You must enter a single upper case character!\nTry replacing the user and try again!');
    uiwait(warndlg(message));
end

[Maureen O'Brien]

The more I think about it, I want to make a function that will check to make sure the input is only one character. So while I appreciate the idea, that's not exactly the way that I want to go about it.

[Image Analyst]

Then use length():

if length(variablename) > 1
    % User entered a response that was too long.

Answer 2

[James Tursa]

Maybe this FEX submission by Jos is close to what you want:

http://www.mathworks.com/matlabcentral/fileexchange/7465-getkey