multilevel df.ix fails with IndexError on Multindex with duplicate entries
The following example works:

df = DataFrame(np.arange(20).reshape(5,4))
df2 = df.set_index(keys=[0,1,2])
df2.ix[(4,5,6)]

for using a MultiIndex

So I created a file sample_data.csv that looks like this:

col1,col2,year,amount 
111111,3.5,2012,700 
111112,3.5,2011,600 
222221,4.0,2012,222 
... 

I then ran the following:

import numpy as np 
import pandas as pd 
sd=pd.read_csv('sample_data.csv') 
sd2=sd.set_index(keys=['col2','year']) 
sd2.ix[(4.0,2012)] 

But this produces the following error: IndexError: index out of bounds
Can anyone explain why the former example works, but the latter doesn't ?
