title: Replace NA in all columns of a dplyr chain
body: <p>The question <a href="https://stackoverflow.com/questions/21714867/replace-na-in-a-dplyr-chain">replace NA in a dplyr chain</a> results into the solution </p>
  
  <pre><code>dt %.% group_by(a) %.% mutate(b = ifelse(is.na(b), mean(b, na.rm = T), b))
  </code></pre>
  
  <p>with dplyr. I want to impute all colums with dplyr chain. There is no single column to group by, rather I want all numeric columns to have all NAs replaced by the means such as column means.</p>
  
  <p><strong>What is the most elegant way to replace all NAs with column means with tidyverse/dp?</strong></p>