array数组
numpy中最基本的类型是array. 其相关操作都是按元素操作的(+, -, *, /等),
举例:
fatansy@fantasy:Ex1_Linear_regression$ ipython
Python 2.7.8 (default, Jun 18 2015, 18:54:19)
Type "copyright", "credits" or "license" for more information.
IPython 3.2.0 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: import numpy as np
In [2]: a = np.arr
np.array np.array2string np.array_equal np.array_equiv np.array_repr np.array_split np.array_str
In [2]: a = np.array([1,2])
In [3]: a
Out[3]: array([1, 2])
In [4]: b = np.array([2,3])
In [5]: b
Out[5]: array([2, 3])
In [6]: c = a * b
In [7]: c
Out[7]: array([2, 6])
In [8]: np.dot(a, b)
Out[8]: 8
注: 两个array相乘*指的是对应元素相乘;
两个array的dot表示矩阵相乘
- 若a是array, 那么a.T表示转置
- 把array转为matrix, 使用asmatrix()
- 多数numpy函数返回的是array类型,不是matrix类型
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