Problem 6.2. Flight Cancellations by Month.

In this problem, you will use Panda's groupby() and aggregate() functions to compute and plot the number of flight cancellations in each month of 2001.



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%matplotlib inline
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

First, write a function named get_month_cancelled() that takes a filename (str) and returns a pd.DataFrame that is indexed by the names of the months and has only one column Cancelled, the number of flight cancellations in each month.

Don't forget to set the encoding option.
Again, if you try to read in all 29 columns, your code will be very slow. Use usecols to read only two columns, Month and Cancelled.
If you don't set the indices, they will be just numbers, e.g. 0, 1, 2... Use the following list to set the indices. Copy/paste (rather than type) since even a single typo will cause problems for autograding.
```
['January', 'February', 'March', 'April', 'May', 'June',
 'July', 'August', 'September', 'October', 'November', 'December']
```

When you call `get_month_cancelled('2001.csv'), you should get the following DataFrame.

             Cancelled
  January        19891
  February       17448
  March          17876
  April          11414
  May             9452
  June           15509
  July           11286
  August         13318
  September      99324
  October         6850
  November        4497
  December        4333

  [12 rows x 1 columns]

The %%writefile magic writes the get_month_cancelled() function to a file named FirstName_LastName_cancelled.py. Edit the command or rename the file, and upload this file along with your .ipynb file.



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#%%writefile FirstName_LastName_cancelled.py

def get_month_cancelled(filename):
    '''
    Reads the "Month" and "Cancelled" columns of a CSV file
    and returns a Pandas DataFrame with only one column "Cancelled"
    indexed by the months.
    
    Parameters
    ----------
    filename(str): The filename of the CSV file.
    
    Returns
    -------
    pandas.DataFrame: "Cancelled" column, indexed by names of the months
    '''
    
    # your code goes here
    
    return month_cancelled

When you run the following cell, you should get

           Cancelled
January        19891
February       17448
March          17876
April          11414
May             9452
June           15509
July           11286
August         13318
September      99324
October         6850
November        4497
December        4333

[12 rows x 1 columns]



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month_cancelled = get_month_cancelled('/data/airline/2001.csv')
print(month_cancelled)

Run the following cell to plot a bar histogram.



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month_cancelled.plot(kind='bar')



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