repeat和tile擴充陣列

但是很多情況下不需要使用,在進行矩陣加減運算的時候會自動複製

>>> a

array([[1, 2],

       [3, 4],

       [5, 6]])

>>> b

array([1, 2])

>>> a-b

array([[0, 0],

       [2, 2],

       [4, 4]])

用repeat和tile擴充陣列元素，例如

>>> import numpy as np
>>> np.arange(10)
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> a = np.arange(10)
>>> a
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> a.repeat(5)
array([0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4,
       4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 9,
       9, 9, 9, 9])
>>> a
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> np.tile(a,2)
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>>

官方例子：

    >>> from numpy import *  
    >>> a=array([10,20])  
    >>> tile(a,(3,2)) #構造3X2個copy  
    array([[10, 20, 10, 20],  
           [10, 20, 10, 20],  
           [10, 20, 10, 20]])  
    >>> tile(42.0,(3,2))  
    array([[ 42.,  42.],  
           [ 42.,  42.],  
           [ 42.,  42.]])  

    >>> from numpy import *  
    >>> repeat(7.,4)  
    array([ 7.,  7.,  7.,  7.])  
    >>> a=array([10,20])  
    >>> a.repeat([3,2])  
    array([10, 10, 10, 20, 20])  
    >>> repeat(a,[3,2])  
    array([10, 10, 10, 20, 20])  
    >>> a=array([[10,20],[30,40]])  
    >>> a.repeat([3,2],axis=0)  
    array([[10, 20],  
           [10, 20],  
           [10, 20],  
           [30, 40],  
           [30, 40]])  
    >>> a.repeat([3,2],axis=1)  
    array([[10, 10, 10, 20, 20],  
           [30, 30, 30, 40, 40]])