title: How to implement variance function in R
body: <p>I am trying to calculate the variance of a column from a data frame.I know that there are inbuilt functions var() for calculating the variance but I am not sure how to write a function for variance by passing my data frame column as variable.</p>
  
  <pre><code>var(banknote$Length)*((n-1)/n)
  </code></pre>