title: R Group by date to get frequency and use another column to filter
body: <p>I have the following R dataframe.  I would like to get the frequency by date but use the <code>Min</code> column to keep the freq 0 if it is 0.  How should I go about this?</p>
  
  <p>Below is my dataframe:</p>
  
  <pre><code>library(plyr)
  
  df
    Location   Date            Min six endsix seven seventeen starteighteen eighteen
  
  1 location_1 2018-11-21       0 360    415   420      1020          1025     1080
  2 location_1 2018-11-22       0 360    415   420      1020          1025     1080
  3 location_1 2018-11-23     131 360    415   420      1020          1025     1080
  4 location_1 2018-11-24       0 360    415   420      1020          1025     1080
  5 location_1 2018-11-25    1001 360    415   420      1020          1025     1080
  6 location_1 2018-11-25     272 360    415   420      1020          1025     1080
  7 location_1 2018-11-25    1319 360    415   420      1020          1025     1080
  </code></pre>
  
  <p>If I do the following <code>count(location_1, "Date")</code> I get </p>
  
  <pre><code>   Date          freq
  1  2018-11-21    1
  2  2018-11-22    1
  3  2018-11-23    1
  4  2018-11-24    1
  5  2018-11-25    5
  </code></pre>
  
  <p>I would like to do this but if there is a 0 for the <code>Min</code> column have 0 for the frequency like the following:</p>
  
  <pre><code>   Date          freq
  1  2018-11-21    0
  2  2018-11-22    0
  3  2018-11-23    1
  4  2018-11-24    0
  5  2018-11-25    5
  </code></pre>