将每个元素除以NumPy数组中的下一个元素
问题描述：
我希望能够将一维numpy数组中的值除以以下值.例如，我有一个看起来像这样的数组.
What I hope to do is be able to divide a value in a 1 dimensional numpy array by the following value. For example, I have an array that looks like this.
[ 0 20 23 25 27 28 29 30 30 22 20 19 19 19 19 18 18 19 19 19 19 19 ]
我想这样做:
0/20 #0th value divided by 1st value
20/23 #1st value divided by 2nd value
23/25 #2nd value divided by 3rd value
25/27 #3rd value divided by 4th value
etc...
我可以轻松地通过循环来完成此操作，但是我想知道是否有更有效的方法可以执行numpy操作.
I can easily do it through a loop, however I was wondering if there is a more efficient way of doing this with numpy operations.
答
Get two Slices - One from start to last-1, another from start+1 to last and perform element-wise division -
a[:-1]/a[1:]
获得浮点数除法-
np.true_divide(a[:-1],a[1:])
或放入from __future__ import division，然后使用a[:-1]/a[1:].
通过 views 进入输入数组，可以真正有效地访问这些切片用于按元素划分操作.
Being views into the input array, these slices are really efficiently accessed for element-wise division operation.
样品运行-
In [56]: a # Input array
Out[56]: array([96, 81, 48, 53, 18, 92, 79, 43, 13, 69])
In [57]: from __future__ import division
In [58]: a[:-1]/a[1:]
Out[58]:
array([ 1.18518519, 1.6875 , 0.90566038, 2.94444444, 0.19565217,
1.16455696, 1.8372093 , 3.30769231, 0.1884058 ])
In [59]: a[0]/a[1]
Out[59]: 1.1851851851851851
In [60]: a[1]/a[2]
Out[60]: 1.6875
In [61]: a[2]/a[3]
Out[61]: 0.90566037735849059