title: R get last element from str_split
body: <p>I have a R list of strings and I want to get the last element of each</p>
  
  <pre><code>require(stringr)
  
  string_thing &lt;- "I_AM_STRING"
  Split &lt;- str_split(string_thing, "_")
  Split[[1]][length(Split[[1]])]
  </code></pre>
  
  <p>but how can I do this with a list of strings?</p>
  
  <pre><code>require(stringr)
  
  string_thing &lt;- c("I_AM_STRING", "I_AM_ALSO_STRING_THING")
  Split &lt;- str_split(string_thing, "_")
  
  #desired result
  answer &lt;- c("STRING", "THING")
  </code></pre>
  
  <p>Thanks</p>