Question

So, I’m trying to build up a program with MATLAB according to some indications from my teacher and I came up with some obstacles which would give me a better grade if I could get them right. Here they are:

1. The user is asked to insert a string but it can’t have more than 20 characters. If it does, the excedents will be ignored and the string is saved with the first 20 characters the user inserted. How do I ignore the excedents in a string and save it anyway?

2. isletter is a function that tells us if the elements are all letters. In this program, the user is asked to insert a string that needs to include both numbers and letters, so that strings with just letters or just numbers are excluded, and then I’ll use a while to keep asking for a string with these characteristics.

Could you please help me? This is my first semester with MATLAB. Thank you!

Answer 1

If you want to disallow characters other than letters and numbers (i.e. '/@!' or whitespace) and require that the string they enter has to have at least 1 letter and 1 number, then you can use the ISSTRPROP function (which is more general than ISLETTER) to check for other types of characters. The idea to use INPUTDLG to prompt for the string (as suggested in Aabaz’s answer) is a good one, so here’s a nice condensed solution using INPUTDLG that achieves what you want:

answer = '';  %# Initialize answer to be an empty string
while any(~isstrprop(answer, 'alphanum')) || ...  %# Check for alphanumeric chars
      ~any(isletter(answer)) || ...     %# Check for at least 1 letter
      ~any(isstrprop(answer, 'digit'))  %# Check for at least 1 number
  answer = inputdlg('Enter string:');   %# Prompt for input
  answer = answer{1}(1:min(20, end));   %# Trim answer to max of 20 chars
end

Note how the functions MIN and END are used to trim the string to 20 characters.