Programming and Data Types

Searching and Replacing

MATLAB provides several functions for searching and replacing characters in a string. Consider a string named label.

• label = 'Sample 1, 10/28/95';
  

The strrep function performs the standard search-and-replace operation. Use strrep to change the date from '10/28' to '10/30'.

• newlabel = strrep(label,'28','30')
  newlabel =
     Sample 1, 10/30/95
  

findstr returns the starting position of a substring within a longer string. To find all occurrences of the string 'amp' inside label

• position = findstr('amp',label)
  position =
      2
  

The position within label where the only occurrence of 'amp' begins is the second character.

The strtok function returns the characters before the first occurrence of a delimiting character in an input string. The default delimiting characters are the set of whitespace characters. You can use the strtok function to parse a sentence into words; for example,

• function all_words = words(input_string)
  remainder = input_string;
  all_words = '';
  
  while (any(remainder))
    [chopped,remainder] = strtok(remainder);
    all_words = strvcat(all_words,chopped);
  end
  

The strmatch function looks through the rows of a character array or cell array of strings to find strings that begin with a given series of characters. It returns the indices of the rows that begin with these characters.

• maxstrings = strvcat('max','minimax','maximum')
  maxstrings =
     max    
     minimax
     maximum
  
  strmatch('max',maxstrings)
  ans =
       1
       3
  

Categorizing Characters Within a String

Regular Expressions