title: Split a delimited string column in data frame, take only last element in new column
body: <p>This has to be an incredibly easy task (and yeah this will probably be marked as a duplicate) but I can't find ANYWHERE how to do this simply within a dataframe without creating lists from the columns and putting them back. Reproducible code below:</p>
  
  <p>I simply wish to separate the last element in the column df, delimited by comma:</p>
  
  <pre><code>df&lt;- c("Lagos, Nigeria", "United States", "Buckingham Palace, Great Britain", 
     "Madison Square Garden, NY, New York, USA")
  df &lt;- data.frame(df, c(1:length(df)), stringsAsFactors = FALSE)
  
  df$column.desired &lt;- c("Nigeria", "United States", "Great Britain", 
                "USA")            
  </code></pre>