title: checking consecutive rows (greater than or lesser than) of a column
body: <p>I want to compare previous row with current row of a column in a dataframe, and subset the higher value alone after a low value. the data is like this,</p>
  
  <pre><code>    &gt; head(counts[,c(2,10:12)],n = 10)
              event_time CLD_Line1 CLD_Line2 CLD_Line3
  1  2015-05-01 05:34:00       756       325       735
  2  2015-05-01 05:39:00       764       330       742
  3  2015-05-01 05:44:00       773       333       752
  4  2015-05-01 05:49:00       775       339       764
  5  2015-05-01 05:54:00       778       345       768
  6  2015-05-01 05:59:00       778       345       768
  7  2015-05-01 06:04:00         0       346       770
  8  2015-05-01 06:09:00         3       349         4
  9  2015-05-01 06:14:00        11         2         6
  10 2015-05-01 06:19:00        18         7        12
  </code></pre>
  
  <p>any function that checks rows with previous rows of a single column i.e,checking  row1 is greater than or lesser than to row2 , row2 is greater than or lesser than r3 and so on..?</p>