title: creating a new column with logical values if value in another column > 0
body: <p>New to R, so bear with me. I have a dataframe with values</p>
  
  <pre><code>x y
  1 2
  4 4
  5 3
  6 0 
  </code></pre>
  
  <p>I want to create a third column that indicates with TRUE or FALSE whether a value in column y is 0.</p>
  
  <pre><code>x y z
  1 2 TRUE
  0 4 TRUE
  5 3 TRUE
  6 0 FALSE
  </code></pre>