title: Finding maximum value across multiple columns (pmax gives NAs)
body: <p>Using <code>reshape</code> function, I have data that looks something like this:</p>
  
  <pre><code>df1
  
  ID Score1  Score2  Score3
  1  2       3       1
  2  3       2       1
  3  2       1       NA 
  4  1       NA      NA
  </code></pre>
  
  <p>As you can see, some of my score variables have missing values. </p>
  
  <p>I'm interested in finding the maximum score variable for all ID values. When I tried using <code>pmax(df1$Score1,df1$Score2,df1$Score3)</code>, my resulting vector contains NAs. I'm not sure why this is, as I know that my Score1 variable doesn't contain any NAs.</p>
  
  <p>This is what I'd like my output to accomplish:</p>
  
  <pre><code>ID MaxScore
  1  3
  2  3
  3  2
  4  1
  </code></pre>
  
  <p>Thanks</p>