title: How do I count the occurrences of a factor in several columns, grouping by one column?
body: <p>I have a seemingly simple question, but I cannot figure out how to get exactly what I want.</p>
  
  <p>My data looks like this:</p>
  
  <pre><code>      Job     C/C++     Java     Python
    Student     FALSE     TRUE      FALSE
  Developer      TRUE     TRUE       TRUE
  Developer      TRUE     TRUE      FALSE
   Sysadmin      TRUE    FALSE      FALSE
    Student     FALSE     TRUE       TRUE
  </code></pre>
  
  <p>I would like to group by the "Job" column and count the number of <code>TRUE</code>s in each column. My desired output would look like this:</p>
  
  <pre><code>      Job     C/C++     Java     Python
    Student         0        2          1
  Developer         2        2          1 
   Sysadmin         1        0          0
  </code></pre>
  
  <p>Any help would be greatly appreciated.</p>