title: How do I replace all NA with mean in R?
body: <p>I have over 1500 columns in my dataset and 100+ of them contains at least one NA. I know I can replace NAs in a single column by</p>
  
  <pre><code>d$var[is.na(d$var)] &lt;- mean(d$var, na.rm=TRUE)
  </code></pre>
  
  <p>but how do I do this too ALL the NAs in my dataset?</p>
  
  <p>Thank you!</p>