[437]numpy库数组拼接np.concatenate()函数

在实践过程中&＃xff0c;会经常遇到数组拼接的问题&＃xff0c;基于numpy库concatenate是一个非常好用的数组操作函数。

1、concatenate((a1, a2, …), axis&＃61;0)官方文档详解

concatenate(...)concatenate((a1, a2, ...), axis&＃61;0)Join a sequence of arrays along an existing axis.Parameters----------a1, a2, ... : sequence of array_likeThe arrays must have the same shape, except in the dimensioncorresponding to &＃96;axis&＃96; (the first, by default).axis : int, optionalThe axis along which the arrays will be joined. Default is 0.Returns-------res : ndarrayThe concatenated array.See Also--------ma.concatenate : Concatenate function that preserves input masks.array_split : Split an array into multiple sub-arrays of equal ornear-equal size.split : Split array into a list of multiple sub-arrays of equal size.hsplit : Split array into multiple sub-arrays horizontally (column wise)vsplit : Split array into multiple sub-arrays vertically (row wise)dsplit : Split array into multiple sub-arrays along the 3rd axis (depth).stack : Stack a sequence of arrays along a new axis.hstack : Stack arrays in sequence horizontally (column wise)vstack : Stack arrays in sequence vertically (row wise)dstack : Stack arrays in sequence depth wise (along third dimension)


2、Parameters参数

• 传入的参数必须是一个多个数组的元组或者列表

• 另外需要指定拼接的方向&＃xff0c;默认是 axis &＃61; 0&＃xff0c;也就是说对0轴的数组对象进行纵向的拼接&＃xff08;纵向的拼接沿着axis&＃61; 1方向&＃xff09;&＃xff1b;注&＃xff1a;一般axis &＃61; 0&＃xff0c;就是对该轴向的数组进行操作&＃xff0c;操作方向是另外一个轴&＃xff0c;即axis&＃61;1。

In [23]: a &＃61; np.array([[1, 2], [3, 4]])
In [24]: b &＃61; np.array([[5, 6]])
In [25]: np.concatenate((a, b), axis&＃61;0)
Out[25]:
array([[1, 2],[3, 4],[5, 6]])


传入的数组必须具有相同的形状&＃xff0c;这里的相同的形状可以满足在拼接方向axis轴上数组间的形状一致即可

如果对数组对象进行 axis&＃61; 1 轴的拼接&＃xff0c;方向是横向0轴&＃xff0c;a是一个2*2维数组&＃xff0c;axis&＃61; 0轴为2&＃xff0c;b是一个1*2维数组&＃xff0c;axis&＃61; 0 是1&＃xff0c;两者的形状不等&＃xff0c;这时会报错

In [27]: np.concatenate((a,b),axis &＃61; 1)
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
in ()
----> 1 np.concatenate((a,b),axis &＃61; 1)ValueError: all the input array dimensions except for the concatenation axis must match exactly


将b进行转置&＃xff0c;得到b为2*1维数组&＃xff1a;

In [28]: np.concatenate((a,b.T),axis &＃61; 1)
Out[28]:
array([[1, 2, 5],[3, 4, 6]])