title: Using if_else, I can't return the column used as the conditional if the conditional is false
body: <p>I've created a <code>flag</code> variable of different job descriptions in a dataset.  I would like to change the each <code>flag==true</code> into the same row position from another variable.  </p>
  
  <p>I've tried <code>ifelse</code> and <code>if_else;</code> but all I've been able to get is a list of the changed values for the <code>true</code> conditional and <code>NA</code>s. </p>
  
  <p>Here is a reproducible example using <code>diamonds</code>:</p>
  
  <pre><code>mydata &lt;- diamonds[1:10,c(3,4)] 
  mydata$position &lt;- c('flag','cathy')
  mydata
  mydata$new.vary &lt;- mydata %&gt;% if_else(color=='E',position,color)
  </code></pre>