title: py/pandas dataframe - how to change daily closing prices into monthly closing prices?
body: <p>My pandas dataframe looks like this:</p>
  
  <pre><code>            VTI       VOO       VGK      IEV
  2017-06-20  125.5809  224.3456  55.2675  44.43
  2017-06-21  125.1100  223.5591  54.8000  44.05
  2017-06-22  124.7800  223.1609  54.8200  44.06
  2017-06-23  124.8100  223.1200  54.8400  44.10
  </code></pre>
  
  <p>i run</p>
  
  <pre><code>m_price = price.resample('BM', how=lambda x: x[-1])
  </code></pre>
  
  <p>which works but tells me: "FutureWarning: how in .resample() is deprecated
  the new syntax is .resample(...)..apply()"</p>
  
  <p>can someone please help me with the new syntax? Thanks
  (Py 3.6.1 / Pandas 0.20.2)</p>