title: Removing rows with the same timestamp numpy
body: <p>I have a numpy array of the form</p>
  
  <pre><code>TimeStamp  Col1 Col2
  0           1    1.2
  0           1.1  1.1
  1           2    3
  1           2.3  3.1
  2           2.2  3.0 
  3           3    4
  </code></pre>
  
  <p>The final array I want is without duplicated time stamp. For a given timestamp I want the last known value. For instance, the output is</p>
  
  <pre><code>TimeStamp      Col1    Col2        
      0           1.1     1.1       
      1           2.3     3.1
      2           2.2     3.0 
      3           3       4
  </code></pre>
  
  <p>I can obviously do this in a clunky for loop. But was curious to find a more elegant numpy solution. Thanks.</p>