title: Is there a way in R to count the number of substrings in a string enclosed in square brackets, all substrings are separated by commas and are quoted?
body: <p>['ax', 'byc', 'crm', 'dop']</p>
  <p>This is a character string, and I want a count of all substrings, ie 4 here as output. Want to do this for the entire column containing such strings.</p>