title: Pandas - How to pass column name in function
body: <p>I might be missing something very simple here but I have a function that plots histograms for a certain column from a Pandas dataframe in certain time spans.  In my function I want to pass the column name as an argument.  This is what I have so far.</p>
  
  <pre><code>def make_hist(data,column_name):
  
      start=datetime(2013,11,1)
      end=datetime(2013,11,30)
      rng=pd.date_range(start,end)
  
      start2=datetime(2013,10,1)
      end2=datetime(2013,10,30)
      rng2=pd.date_range(start2,end2)
  
      start3=datetime(2013,9,1)
      end3=datetime(2013,9,30)
      rng3=pd.date_range(start3,end3)
  
  
      start4=datetime(2013,8,1)
      end4=datetime(2013,8,30)
      rng4=pd.date_range(start4,end4)
  
      start5=datetime(2013,7,1)
      end5=datetime(2013,7,30)
      rng5=pd.date_range(start5,end5)
  
  
      start6=datetime(2013,12,1)
      end6=datetime(2013,12,30)
      rng6=pd.date_range(start6,end6)
  
      plt.subplot(611)
      data.ix[rng6].column_name.hist(bins=[0,30,60,90,120,150,180,210,240,270,300]).plot()
      plt.title('December')
      plt.ylim(0,300)
      plt.xlim(0,300)
      plt.subplot(612)
      data.ix[rng].column_name.hist(bins=[0,30,60,90,120,150,180,210,240,270,300]).plot()
      plt.title('November')
      plt.ylim(0,300)
      plt.xlim(0,300)
      plt.subplot(613)
      data.ix[rng2].column_name.hist(bins=[0,30,60,90,120,150,180,210,240,270,300]).plot()
      plt.title('October')
      plt.ylim(0,300)
      plt.xlim(0,300)
      plt.subplot(614)
      data.ix[rng3].column_name.hist(bins=[0,30,60,90,120,150,180,210,240,270,300]).plot()
      plt.title('September')
      plt.ylim(0,300)
      plt.xlim(0,300)
      plt.subplot(615)
      data.ix[rng4].column_name.hist(bins=[0,30,60,90,120,150,180,210,240,270,300]).plot()
      plt.title('August')
      plt.ylim(0,300)
      plt.xlim(0,300)
      plt.subplot(616)
      data.ix[rng5].column_name.hist(bins=[0,30,60,90,120,150,180,210,240,270,300]).plot()
      plt.title('July')
      plt.ylim(0,300)
      plt.xlim(0,300)
      plt.show()
  </code></pre>
  
  <p>The problem is that I do not know what data type the argument <code>column_name</code> should be.  It cannot be a string and it cannot just be a variable because I do not know how I would define it.  I feel like there is a simple way to do this that I am just not seeing.</p>
  
  <p>EDIT: adding a description of the dataframe.  The output of <code>data.dtypes</code> is </p>
  
  <pre><code>account                             int64
  first_active                       object
  datelatest_inactive        datetime64[ns]
  days_active                         int64
  dtype: object
  </code></pre>
  
  <p>and my index is on the <code>datelatest_inactive</code> column</p>