跟numpy.random.seed()一样刚开始理解都是很头疼的存在,但其实他们的用法几乎一样(如果有人对seed()有疑问的话可以看我的另一篇讲解:【数据处理】Numpy.random.seed()的用法 ):
numpy.random.RandomState()是一个伪随机数生成器。那么伪随机数是什么呢?
伪随机数是用确定性的算法计算出来的似来自[0,1]均匀分布的随机数序列。并不真正的随机,但具有类似于随机数的统计特征,如均匀性、独立性等。(摘自《百度百科》)
下面我们来看看它的用法:
import numpy as np
rng = np.random.RandomState(0) rng.rand(4) Out[377]: array([0.5488135 , 0.71518937, 0.60276338, 0.54488318]) rng = np.random.RandomState(0) rng.rand(4) Out[379]: array([0.5488135 , 0.71518937, 0.60276338, 0.54488318])
看,是不是生成了一样的随机数组呢,这点和numpy.random.seed()还是很一样的,
因为是伪随机数,所以必须在rng这个变量下使用,如果不这样做,那么就得不到相同的随机数组了,即便你再次输入了numpy.random.RandomState():
np.random.RandomState(0) Out[397]: <mtrand.RandomState at 0xddaa288> np.random.rand(4) Out[398]: array([0.62395295, 0.1156184 , 0.31728548, 0.41482621]) np.random.RandomState(0) Out[399]: <mtrand.RandomState at 0xddaac38> np.random.rand(4) Out[400]: array([0.86630916, 0.25045537, 0.48303426, 0.98555979])
这是因为np.random.rand()在默认状态下,是从默认随机数组里挑出的随机样本。
rng = np.random.RandomState(0) x = rng.randn(4) y = rng.randn(4) x Out[393]: array([1.76405235, 0.40015721, 0.97873798, 2.2408932 ]) y Out[394]: array([ 1.86755799, -0.97727788, 0.95008842, -0.15135721])下面给出两个自定义函数来帮助更好地理解:
def rng1(): for i in range(4): rng = np.random.RandomState(0) print("i = ",i) print(rng.rand(3,2)) rng1()
i = 0 [[0.5488135 0.71518937] [0.60276338 0.54488318] [0.4236548 0.64589411]] i = 1 [[0.5488135 0.71518937] [0.60276338 0.54488318] [0.4236548 0.64589411]] i = 2 [[0.5488135 0.71518937] [0.60276338 0.54488318] [0.4236548 0.64589411]] i = 3 [[0.5488135 0.71518937] [0.60276338 0.54488318] [0.4236548 0.64589411]]
def rng2(): rng = np.random.RandomState(0) for i in range(4): print("i = ",i) print(rng.rand(3,2)) rng2()
i = 0 [[0.5488135 0.71518937] [0.60276338 0.54488318] [0.4236548 0.64589411]] i = 1 [[0.43758721 0.891773 ] [0.96366276 0.38344152] [0.79172504 0.52889492]] i = 2 [[0.56804456 0.92559664] [0.07103606 0.0871293 ] [0.0202184 0.83261985]] i = 3 [[0.77815675 0.87001215] [0.97861834 0.79915856] [0.46147936 0.78052918]]大家现在对这个函数是不是理解很多了呢。