title: summary still shows NAs after using both na.omit and complete.cases
body: <p>I am a grad student using R and have been reading the other Stack Overflow answers regarding removing rows that contain NA from dataframes.  I have tried both na.omit and complete.cases.  When using both it shows that the rows with NA have been removed, but when I write summary(data.frame) it still includes the NAs.  Are the rows with NA actually removed or am I doing this wrong?</p>
  
  <pre><code>na.omit(Perios)
  summary(Perios)
  
  Perios[complete.cases(Perios),]
  summary(Perios)
  </code></pre>