如何删除字符串，matlab之间的额外空格？

Question

I have created a script to convert text to morsecode, and now I want to modify it to include a slash between words.So something like space slash space between morsecode words. I know my loop before the main loop is incorrect and I want to fix it to do as stated before I just really need help Thank You!!!:

...

Word=input('Please enter a word:','s');
  ...
             Code=MC_1;
    ...

    case ' '
         Code='/'
    otherwise 
         Valid=0;
end
if Valid
         fprintf('%s ',Code);
else
         disp('Input has invalid characters!')
         break
end

Answer 1

I know you want to write a loop to remove multiple spaces in between words, but the best way to remove white space in your particular problem would be to use regular expressions , specifically with regexprep . Regular expressions are used to search for particular patterns / substrings within a larger string. In this case, what we are trying to find are substrings that consist of more than one whitespace. regexprep finds substrings that match a pattern, and replaces them with another string. In our case, you would search for any substrings within your string that contain at least one more whitespace characters, and replace them with a single whitespace character. Also, I see that you've trimmed both leading and trailing whitespace for the string using strtrim , which is great. Now, all you need to do is call regexprep like so:

Word = regexprep(Word, '\s+', ' ');

\\s+ is the regular expression for finding at least one white space character . We then replace this with a single whitespace. As such, supposing we had this string stored in Word :

Word = '   hello    how    are   you   ';

Doing a trim of leading and trailing whitespace, then calling regexprep in the way we talked about thus gives:

Word = strtrim(Word);
Word = regexprep(Word, '\s+', ' ')

Word =

hello how are you

As you can see, the leading and trailing white space was removed with strtrim , and the regular expression takes care of the rest of the spaces in between.

---

However, if you are dead set on using a loop, what you can do is use a logical variable which is set to true when we detect a white space, and then we use this variable and skip other white space characters until we hit a character that isn't a space. We would then place our space, then / , then space, then continue. In other words, do something like this:

Word = strtrim(Word); %// Remove leading and trailing whitespace
space_hit = false; %// Initialize space encountered flag
Word_noSpace = []; %// Will store our new string
for index=1:length(Word) %// For each character in our word
    if Word(index) == ' ' %// If we hit a space
       if space_hit %// Check to see if we have already hit a space
          continue; %// Continue if we have
       else
          Word_noSpace = [Word_noSpace ' ']; %// If not, add a space, then set the flag
          space_hit = true;
       end
    else
       space_hit = false; %// When we finally hit a non-space, set back to false
       Word_noSpace = [Word_noSpace Word(index)]; %// Keep appending characters
    end
end
Word = Word_noSpace; %// Replace to make compatible with the rest of your code

for Character = Word %// Your code begins here
   ...
   ...

What the above code does is that we have an empty string called Word_noSpace that will contain our word with no extra spaces, and those spaces replaced with a single whitespace. The loop goes through each character, and should we encounter a space, we check to see if we have already encountered a space. If we have, just continue on in the loop. If we haven't, then concatenate a whitespace. Once we finally hit a non-space character, we simply just add those characters that are not spaces to this new string. The result will be a string with no extra spaces, and those are replaced with a single white space.

Running the above code after you trim the leading and trailing white space thus gives:

Word =

hello how are you