title: Why do I get "warning longer object length is not a multiple of shorter object length"?
body: <p>I have dataframe dih_y2. These two lines give me a warning:</p>
  
  <pre><code>&gt; memb = dih_y2$MemberID[1:10]
  &gt; dih_col = which(dih_y2$MemberID == memb)  
  Warning message:
  In dih_y2$MemberID == memb :
  longer object length is not a multiple of shorter object length
  </code></pre>
  
  <p>Why?</p>