title: Filtering data in R
body: <p>I have a CSV of file of data that I can load in R using <code>read.csv()</code></p>
  
  <p>Some of the data is missing, so I want to reduce the data frame down to set that consists entirely of non-missing data, i.e. if a <code>NULL</code> appears anywhere, I want to exclude that column and row from the filtered data set.</p>
  
  <p>I know I can probably do this fairly simply with the inbuilt R vector operations, but I am not quite sure how to do this exactly?</p>
  
  <p>To make my question a little more concrete, here is a quick sample of the data so you can see what I want to do.</p>
  
  <pre><code>DocID       Anno1    Anno7  Anno8
  1           7        NULL   8
  2           8        NULL   3
  44          10       2      3
  45          6        6      6
  46          1        3      4
  49          3        8      5
  62          4        NULL   9
  63          2        NULL   4
  67          11       NULL   3
  91          NULL     9      7
  92          NULL     7      5
  93          NULL     8      8
  </code></pre>
  
  <p>So given this input, I need some code that will reduce the output to this.</p>
  
  <pre><code>DocID       Anno8
  44          3
  45          6
  46          4
  49          5
  </code></pre>
  
  <p>As <code>Anno8</code> is the only column with non-NULL data, and there are only four rows with non-NULL data.</p>