title: How to find maximum string length by column in data frame
body: <p>My question is similar <a href="https://stackoverflow.com/questions/24212739/how-to-find-the-highest-value-of-a-column-in-a-data-frame-in-r">to this</a>. But for strings.</p>
  
  <p>So I have a dataframe, each column contains strings of different length. So, how I can find the maximum string length per column? </p>
  
  <p>Then, how to select the columns, where length is > 1, by <em>sapply</em> or similar.</p>
  
  <p>A typical column of the dataframe looks like this:</p>
  
  <pre><code>clmn=c("XDX", "GUV", "FQ", "ACUE", "HIT", "AYX", "NFD", "AHBW", "GKQ", "PYF")
  </code></pre>
  
  <p>Thanks</p>