udacity 机器学习课程

MODE 众数

mean 均值

median 中位数

standard deviation 标准差

numpy：

    import numpy as np

    array_1 = np.array([[1, 2], [3, 4]], float)
    array_2 = np.array([[5, 6], [7, 8]], float)
    print array_1 + array_2
    print ""
    print array_1 - array_2
    print ""
    print array_1 * array_2

    array_1 = np.array([1, 2, 3], float)
    array_2 = np.array([[6], [7], [8]], float)
    print np.mean(array_1)
    print np.mean(array_2)
    print ""
    print np.dot(array_1, array_2)

np.dot

Pandas:

创建一个Series：

import pandas as pd
series = pd.Series([‘Dave‘, ‘Cheng-Han‘, ‘Udacity‘, 42, -1789710578])
print series

cuteness = pd.Series([1, 2, 3, 4, 5], index=[‘Cockroach‘, ‘Fish‘, ‘Mini Pig‘,
                                                 ‘Puppy‘, ‘Kitten‘])
print cuteness > 3
print ""
print cuteness[cuteness > 3]

创建一个数据框，DataFram

    data = {‘year‘: [2010, 2011, 2012, 2011, 2012, 2010, 2011, 2012],
            ‘team‘: [‘Bears‘, ‘Bears‘, ‘Bears‘, ‘Packers‘, ‘Packers‘, ‘Lions‘,
                     ‘Lions‘, ‘Lions‘],
            ‘wins‘: [11, 8, 10, 15, 11, 6, 10, 4],
            ‘losses‘: [5, 8, 6, 1, 5, 10, 6, 12]}
    football = pd.DataFrame(data)
    print football

    print football.dtypes
    print ""
    print football.describe()
    print ""
    print football.head()
    print ""
    print football.tail()

data = {‘year‘: [2010, 2011, 2012, 2011, 2012, 2010, 2011, 2012],
            ‘team‘: [‘Bears‘, ‘Bears‘, ‘Bears‘, ‘Packers‘, ‘Packers‘, ‘Lions‘,
                     ‘Lions‘, ‘Lions‘],
            ‘wins‘: [11, 8, 10, 15, 11, 6, 10, 4],
            ‘losses‘: [5, 8, 6, 1, 5, 10, 6, 12]}
football = pd.DataFrame(data)
print football[‘year‘]
print ‘‘
print football.year  # shorthand for football[‘year‘]
print ‘‘
print football[[‘year‘, ‘wins‘, ‘losses‘]]   #显示year,wins,losses,列

print football.iloc[[0]]    #显示第一行
print football[3:5]
print football[football.wins > 10]  #打印wins大于10的数据
print football[(football.wins > 10) & (football.team == "Packers")]