Matplotlib plot is a no-show

When I run this code

    import pandas as pd
    import numpy as np
    def add_prop(group):
        births = group.births.astype(float)
        group['prop'] = births/births.sum()
        return group

    pieces = []
    columns = ['name', 'sex', 'births']

    for year in range(1880, 2012):
        path = 'yob%d.txt' % year
        frame = pd.read_csv(path, names = columns)
        frame['year'] = year
        names = pd.concat(pieces, ignore_index = True)

    total_births = names.pivot_table('births', rows = 'year', cols = 'sex', aggfunc = sum)
    total_births.plot(title = 'Total Births by sex and year')

I get no plot. This is from Wes McKinney's book on using Python for data analysis. Can anyone point me in the right direction?


    import matplotlib.pyplot as plt

at the top, and

at the end.