title: How do I get the tabulate() function in R to include the value of zero? Are there other options?
body: <p>I have a test data set called "predicted" that results after taking 100 bootstrap samples from a random normal distribution. Predicted is filled with integer data (from 0 to 20).</p>
  
  <p>When I use the following function:</p>
  
  <pre><code>predicted_output &lt;- as.matrix(tabulate(predicted, 
      nbins = max(0, predicted, na.rm = FALSE)))
  </code></pre>
  
  <p>I observe that all counts associated with [0,] are excluded from the resulting matrix (as per the description in the tabulate data, which notes that NAs are (silently) ignored). How do I (or can I) augment tabulate to provide a matrix which, in my case, has 21 rows, and includes the counts for the NULL values?</p>