title: How to remove footnote references from a column in R?
body: <p>probably a pretty basic question. I'm trying to analyse a data set that includes a column with footnote references in square brackets. I hope to remove these but I cannot seem to find the appropriate function/pattern to remove both them and the numbers inside the brackets.</p>
  
  <p>Likewise, I would like take the <em>median</em> of those entries which have two numbers, e.g. "5930 – 6970[13]" and thereafter <em>divide</em> all entries by 1000.</p>
  
  <pre><code>              "1800[10]"         "3300 – 12 000[11]"       "5000 – 6000[12]"      
         "5930 – 6970[13]"       "75 000 – 80 000[14]"            "93 000[15]"           
   "195 000 – 210 000[16]"               "530 000[17]"           "595 000[18]"      
  </code></pre>
  
  <p>Any help will be highly appreciated.</p>