title: fill a heat map (24h by 7days) in ggplot2
body: <p>I have bike data that looks like this - the dimensions of the data frame are large. </p>
  
  <pre>
  > dim(All_2014)
  [1] 994367     10
  > head(All_2014)
    X bikeid end.station.id start.station.id diff.time            stoptime           starttime
  1 1  16379            285              356    338387 2014-01-02 15:22:28 2014-01-06 13:22:15
  2 2  16379            361              146     47631 2014-01-09 22:45:34 2014-01-10 11:59:25
  3 3  16379            268              327      5089 2014-01-10 12:35:22 2014-01-10 14:00:11
  4 4  16379            398              324    715924 2014-01-22 14:34:55 2014-01-30 21:26:59
  5 5  15611            536              445    716031 2014-01-02 15:30:44 2014-01-10 22:24:35
  6 6  15611            348              433     68544 2014-01-12 14:03:01 2014-01-13 09:05:25
                midtime Hour      Day
  1 2014-01-04 14:22:21   14 Saturday
  2 2014-01-10 05:22:29    5   Friday
  3 2014-01-10 13:17:46   13   Friday
  4 2014-01-26 18:00:57   18   Sunday
  5 2014-01-06 18:57:39   18   Monday
  6 2014-01-12 23:34:13   23   Sunday
  
  </pre>
  
  <p>My aim is to create a heat map using <code>ggplot2</code> (or another package if it is better suited) that looks like this one, where day of the week is on the y-axis and hour is on the x-axis (the hour does not have to be in AM/PM, it can remain as is on the 24-hour scale.: <a href="https://i.stack.imgur.com/sFz0T.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sFz0T.png" alt="enter image description here"></a></p>
  
  <p>The fill of the boxes is a percentage that represents the amount of rides taken within a given hour-interval/the total rides on that day of the week.  I have managed to get this far with the data, but would like to know the easiest way to find percentages and then, how to create a heat map with them. </p>