Python Numpy diff倒置手术?
使用函数时,假设以下简单情况:Python Numpy diff倒置手术?,python,numpy,diff,Python,Numpy,Diff,使用函数时,假设以下简单情况: >>> x = np.array([1, 2, 4, 7, 0]) >>> x_diff = np.diff(x) array([ 1, 2, 3, -7]) 我怎样才能轻松地将x恢复到原始比例而不差分?我想其中有一个元素。与第一个元素连接,然后使用- 对于串联,我们也可以使用np.hstack,如下所示- np.hstack((x[0], x_diff)).cumsum() 或者使用np.concatenate进行连接
>>> x = np.array([1, 2, 4, 7, 0])
>>> x_diff = np.diff(x)
array([ 1, 2, 3, -7])
我怎样才能轻松地将x恢复到原始比例而不差分?我想其中有一个元素。与第一个元素连接,然后使用- 对于串联,我们也可以使用
np.hstack
,如下所示-
np.hstack((x[0], x_diff)).cumsum()
或者使用np.concatenate
进行连接-
np.concatenate(([x[0]], x_diff)).cumsum()
绩效基准
Divakar提出了一些解决方案,我想知道,我应该采取什么措施,这里是性能基准。我还补充了答案
结果
长话短说-只需使用:np.concatenate(([x[0]],x_diff)).cumsum()
x:问题大小,y:1000次运行的计算时间
代码
输出
np.concatenate(([x[0]], x_diff)).cumsum()
import timeit
import random
import numpy as np
import matplotlib.pyplot as plt
cmds = [
'np.r_[x[0], x_diff].cumsum()',
'np.hstack((x[0], x_diff)).cumsum()',
'np.concatenate(([x[0]], x_diff)).cumsum()',
'csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])',
]
test_range = [1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6]
# test_range = [1e0, 1e1, 1e2]
ts = np.empty((len(cmds), len(test_range)), dtype=float)
for tt, size_float in enumerate(test_range):
size = round(size_float)
print('array size:', size)
x = np.random.randint(low=0, high=100, size=size)
x_diff = np.diff(x)
n_trials = 1000
for cc, cmd in enumerate(cmds):
t = timeit.Timer(cmd, globals={**globals(), **locals()})
t = t.timeit(n_trials)
ts[cc, tt] = t
print('time for {:d}x \"{:}\": {:.6f}'.format(n_trials, cmd, t))
fig, ax = plt.subplots(1, 1, figsize=(15, 10))
for cc, cmd in enumerate(cmds):
ax.plot(test_range, ts[cc, :], label=cmd)
print(cmd)
ax.legend()
ax.set_xscale('log')
ax.set_yscale('log')
array size: 1
time for 1000x "np.r_[x[0], x_diff].cumsum()": 0.011935
time for 1000x "np.hstack((x[0], x_diff)).cumsum()": 0.006159
time for 1000x "np.concatenate(([x[0]], x_diff)).cumsum()": 0.003221
time for 1000x "csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])": 0.003482
array size: 10
time for 1000x "np.r_[x[0], x_diff].cumsum()": 0.009031
time for 1000x "np.hstack((x[0], x_diff)).cumsum()": 0.006170
time for 1000x "np.concatenate(([x[0]], x_diff)).cumsum()": 0.003082
time for 1000x "csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])": 0.003467
array size: 100
time for 1000x "np.r_[x[0], x_diff].cumsum()": 0.009754
time for 1000x "np.hstack((x[0], x_diff)).cumsum()": 0.006332
time for 1000x "np.concatenate(([x[0]], x_diff)).cumsum()": 0.003296
time for 1000x "csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])": 0.004249
array size: 1000
time for 1000x "np.r_[x[0], x_diff].cumsum()": 0.010550
time for 1000x "np.hstack((x[0], x_diff)).cumsum()": 0.008595
time for 1000x "np.concatenate(([x[0]], x_diff)).cumsum()": 0.005414
time for 1000x "csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])": 0.006916
array size: 10000
time for 1000x "np.r_[x[0], x_diff].cumsum()": 0.029658
time for 1000x "np.hstack((x[0], x_diff)).cumsum()": 0.028389
time for 1000x "np.concatenate(([x[0]], x_diff)).cumsum()": 0.024410
time for 1000x "csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])": 0.034652
array size: 100000
time for 1000x "np.r_[x[0], x_diff].cumsum()": 0.221405
time for 1000x "np.hstack((x[0], x_diff)).cumsum()": 0.219564
time for 1000x "np.concatenate(([x[0]], x_diff)).cumsum()": 0.215796
time for 1000x "csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])": 0.310225
array size: 1000000
time for 1000x "np.r_[x[0], x_diff].cumsum()": 2.660822
time for 1000x "np.hstack((x[0], x_diff)).cumsum()": 2.664244
time for 1000x "np.concatenate(([x[0]], x_diff)).cumsum()": 2.636382
time for 1000x "csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])": 3.770557
np.r_[x[0], x_diff].cumsum()
np.hstack((x[0], x_diff)).cumsum()
np.concatenate(([x[0]], x_diff)).cumsum()
csp0 = np.zeros(shape=(len(x) + 1,)); np.cumsum(x, out=csp0[1:])