title: left join function help in R
body: <p>Is it possible, to lookup values via left join that have different column names in the data set, but have the same values. </p>
  
  <p>For example, In dataframe x, I have a variable email but in dataframe y my column name could be username but store emails ids</p>
  
  <pre><code>x
  email
  abcd@gmail.com
  efg@gmmail.com
  
  y
  username
  abcd@gmail.com
  xyz@gmail.com
  </code></pre>
  
  <p>This what I would have used if both x&amp;y had same column names, but this scenario is different.</p>
  
  <pre><code>library(dplyr)
  z &lt;- left_join(x, y, by = "email", copy = FALSE)
  </code></pre>