title: R merging rows in a dataframe
body: <p>Here is the <code>head</code> of a large data frame</p>
  
  <pre><code>head(Hdata_soil)
                        X_id           timestamp address rssi batt_v soil_temp_1 soil_temp_2 soil_temp_3 soil_moisture_1
  1 565846060dd8e408e3817c58 2015-11-27 12:01:10      A8  -65     NA          NA          NA          NA              NA
  2 565846070dd8e408e3817c59 2015-11-27 12:01:11      A8   NA     NA        9.73     -273.15       14.63             647
  3 565846cf0dd8e408e3817caf 2015-11-27 12:04:31      A7  -64     NA          NA          NA          NA              NA
  4 565846cf0dd8e408e3817cb0 2015-11-27 12:04:31      A7   NA     NA        8.56        9.46        9.64             660
  5 565847650dd8e408e3817cf5 2015-11-27 12:07:01      A8  -64     NA          NA          NA          NA              NA
  6 565847660dd8e408e3817cf6 2015-11-27 12:07:02      A8   NA     NA        9.82     -273.15       14.29             643
  </code></pre>
  
  <p>The full data set can be accessed from <a href="https://www.dropbox.com/s/75qd4ulfj9ou3kk/Hdata_soil.csv?dl=0" rel="nofollow">dropbox</a></p>
  
  <p>As you can see there are 2 consecutive observations for each <code>address</code> with <code>timestamps</code> approx 1 s apart. The variables are split between these 2 observations. How can I go about merging them in to one row, conserving the first <code>timestamp</code>? </p>
  
  <p>It would also be great to make sure that this only happen with 2 consecutive observations from the same <code>address</code>.</p>
  
  <p>I would really appreciate it if someone could point me in the right direction with regards to packages /functions to use.</p>