def main():
pregnancies = first.get_pregnancies_dataset()
live_pregnancies = [preg for preg in pregnancies.records if preg.outcome == 1]
firsts, subsequents = first.split_one_vs_all(live_pregnancies,
birthord=1)
period_first = first.get_values_for_field(firsts, 'prglength')
period_subsequent = first.get_values_for_field(subsequents, 'prglength')
var_first = thinkstats.Var(period_first)
var_second = thinkstats.Var(period_subsequent)
print('Variance of the first children gestation periods: {} weeks^2'
.format(var_first))
print('\tAnd the sd is {} weeks.'.format(math.sqrt(var_first)))
print('Variance of the subsequent children gestation periods: {} weeks^2'
.format(var_second))
print('\tAnd the sd is {} weeks.'.format(math.sqrt(var_second)))
weights = get_pumpkin_weights()
print('Finding the variance and mean for these pumpkins: {}'
.format(weights))
mu, var = pumpkins(weights)
sd = math.sqrt(var)
print('\tmean = {}\tvariance = {}\tsd = {}'.format(mu, var, sd))
bar_chart(pregnancies)
plot_pregnancy_pmf(pregnancies)
plot_pregnancies_pmf_differences(pregnancies)
def bar_chart(pregnancies):
live_pregnancies = first.get_live_pregnancies(pregnancies)
firsts, seconds = first.split_one_vs_all(live_pregnancies, birthord=1)
period_first = first.get_values_for_field(firsts, 'prglength')
period_second = first.get_values_for_field(seconds, 'prglength')
hist1 = pmf.MakeHistFromList(period_first)
hist2 = pmf.MakeHistFromList(period_second)
fig = plt.figure()
ax = fig.add_subplot(111)
width = 0.35
x1, y1 = hist1.Render()
x2, y2 = hist2.Render()
r1 = ax.bar(x1, y1, width, color='blue')
r2 = ax.bar(np.array(x2) + width, y2, width, color='grey')
ax.set_xlabel('Gestation period(weeks)')
ax.set_ylabel('Frequency')
ax.set_title('Comparison of the gestation periods of first and subsequent'
' babies')
ax.legend((r1[0], r2[0]), ('First Babies', 'Subsequent Babies'))
plt.show()
