title: Row-wise iteration like apply with purrr
body: <p>How do I achieve row-wise iteration using purrr::map?</p>
  
  <p>Here's how I'd do it with a standard row-wise apply.  </p>
  
  <pre><code>df &lt;- data.frame(a = 1:10, b = 11:20, c = 21:30)
  
  lst_result &lt;- apply(df, 1, function(x){
              var1 &lt;- (x[['a']] + x[['b']])
              var2 &lt;- x[['c']]/2
              return(data.frame(var1 = var1, var2 = var2))
            })
  </code></pre>
  
  <p>However, this is not too elegant, and I would rather do it with purrr.  May (or may not) be faster, too.</p>