數(shù)據(jù)應(yīng)用上節(jié)讀取的CSV；
1.值分類匯總

counts = df['hGrade'].value_counts()
print counts

2.繪制柱形圖，并保存

plt = counts.plot(kind='bar').get_figure()
plt
plt.savefig('/Users/baidu/Downloads/plot.png')

3.數(shù)據(jù)分組

#數(shù)據(jù)準(zhǔn)備
import pandas as pd
import numpy as np
df = pd.DataFrame({'A':['foo', 'bar','foo', 'bar', 'foo', 'bar', 'foo', 'foo'],
                  'B':['one', 'one', 'two', 'three', 'two', 'two', 'one', 'three'],
                  'C':np.random.randn(8),
                  'D':np.random.randn(8)})
print df

#根據(jù)列A進(jìn)行分組，取每組第一行數(shù)據(jù)
grouped = df.groupby('A')
print grouped.first()

#根據(jù)多列進(jìn)行分組A，B列
grouped = df.groupby(['A', 'B'])
print grouped.last()

根據(jù)列進(jìn)行分組

def get_type(letter):
    if letter.lower() in 'abem':
        return 'vowel'
    else:
        return 'consonant'
    
grouped = df.groupby(get_type, axis=1)
print grouped.first()