title: How to convert the dataframe to array in python?
body: <p>I have read data from excel like the followings:</p>
  
  <pre><code>import numpy as np
  import pandas as pd
  
  Location = r'C:\temp\test.xlsx'
  data = pd.read_excel(Location, '4bar',     header=0,     parse_cols=0)
  
  data
  Out[80]: 
               10V        11V
  0     -60.531006 -31.539307
  1      -2.547607 -30.776367
  2      58.487549  48.569336
  3      72.220459  74.509277
  4      64.591064  74.509277
  5      54.672852  60.013428
  </code></pre>
  
  <p>I want to put the column '10V' and '11V' into two arrays. In order to process the data with filter coefficients.
  But I don't know how to copy column to array or how to access/operate the element directly in DataFrame?</p>
  
  <p>Can anyone give me a hint?
  Thank you.</p>