title: Create column names with spaces
body: <p>I'm trying to create a DF with columns that contain spaces in their names, but an error is appearing. This is the DF I am trying to create:</p>
  
  <pre><code>CITY &lt;- c('NEW YORK', 'LONDON', 'SAN FRANCISCO', 'MADRID',  'LOS ANGELES', 'LISBON', 'RIO DE JANEIRO', 'MOSCOW',  'SAO PAULO', 'TOKIO')
  NEW YORK &lt;- c(0, 700, 250, 1000, 400, 800, 430, 900, 500, 30)
  LONDON &lt;- c(700, 0, 350, 1200, 50, 110, 780, 984, 1150, 5)
  SAN FRANCISCO &lt;- c(250, 350, 0, 200, 15, 260, 305, 412, 29, 102)
  MADRID &lt;- c(1000, 1200, 200, 0, 77, 115, 225, 318, 412, 511)
  LOS ANGELES &lt;- c(400, 50, 15, 77, 0, 88, 819, 733, 978, 1001)
  LISBON &lt;- c(800, 110, 260, 115, 88, 0, 17, 3000, 1418, 735)
  RIO DE JANEIRO &lt;- c(430, 780, 305, 225, 819, 17, 0, 513, 701, 56)
  MOSCOW &lt;- c(900, 984, 412, 318, 733, 3000, 513, 0, 389, 499)
  SAO PAULO &lt;- c(500, 1150, 29, 412, 978, 1418, 701, 389, 0, 1113)
  TOKIO &lt;- c(30, 5, 102, 511, 1001, 735, 56, 499, 1113, 0)
  DF &lt;- data.frame(CITY, NEW YORK, LONDON, SAN FRANCISCO, MADRID,  LOS ANGELES, LISBON, RIO DE JANEIRO, MOSCOW,  SAO PAULO, TOKIO)
  </code></pre>
  
  <p>This is error message:</p>
  
  <pre><code>Error: unexpected symbol in "NEW YORK"
  </code></pre>
  
  <p>How do I solve this example of my problem? The DF I'm working on has several columns like this example, so I'd like a solution suggestion that could span multiple columns.</p>