title: Transmute over multiple columns in dplyr
body: <p>I have a dplyr question: How do I use <code>transmute</code> over each column without writing each column out by hand? I.e. is there something like <code>transmute_each()</code>?</p>
  
  <p>I want to do the following: Using dplyr I want to get the z-score of each column for a MWE below:</p>
  
  <pre><code>tickers &lt;- c(rep(1,10),rep(2,10))
  df &lt;- data.frame(cbind(tickers,rep(1:20),rep(2:21),rep(2:21),rep(4:23),rep(3:22)))
  colnames(df) &lt;- c("tickers","col1","col2","col3","col4","col5")
  df %&gt;%  group_by(tickers)
  </code></pre>
  
  <p>Is there a simple way to then use transmute to achieve the following:</p>
  
  <pre><code>for(i in 2:ncol(df)){
    df[,i] &lt;- df[,i] - mean(df[,i])/sd(df[,i])
  }
  </code></pre>
  
  <p>Many thanks</p>