随机抽样 (numpy.random)

简单的随机数据

(d0, d1, ..., dn)	随机值 >>> np.random.rand(3,2)array([[ 0.14022471, 0.96360618], #random [ 0.37601032, 0.25528411], #random [ 0.49313049, 0.94909878]]) #random
(d0, d1, ..., dn)	返回一个样本，具有标准正态分布。 Notes For random samples from $N(\mu, \sigma^2)$ , use: sigma * np.random.randn(...) + mu Examples >>> np.random.randn()2.1923875335537315 #random Two-by-four array of samples from N(3, 6.25): >>> 2.5 * np.random.randn(2, 4) + 3array([[-4.49401501, 4.00950034, -1.81814867, 7.29718677], #random [ 0.39924804, 4.68456316, 4.99394529, 4.84057254]]) #random
(low[, high, size])	返回随机的整数，位于半开区间 [low, high)。 >>> np.random.randint(2, size=10)array([1, 0, 0, 0, 1, 1, 0, 0, 1, 0])>>> np.random.randint(1, size=10)array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0]) Generate a 2 x 4 array of ints between 0 and 4, inclusive: >>> np.random.randint(5, size=(2, 4))array([[4, 0, 2, 1], [3, 2, 2, 0]])
(low[, high, size])	返回随机的整数，位于闭区间 [low, high]。 Notes To sample from N evenly spaced floating-point numbers between a and b, use: a + (b - a) * (np.random.random_integers(N) - 1) / (N - 1.) Examples >>> np.random.random_integers(5)4>>> type(np.random.random_integers(5)) >>> np.random.random_integers(5, size=(3.,2.))array([[5, 4], [3, 3], [4, 5]]) Choose five random numbers from the set of five evenly-spaced numbers between 0 and 2.5, inclusive (i.e., from the set ${0, 5/8, 10/8, 15/8, 20/8}$ ): >>> 2.5 * (np.random.random_integers(5, size=(5,)) - 1) / 4.array([ 0.625, 1.25 , 0.625, 0.625, 2.5 ]) Roll two six sided dice 1000 times and sum the results: >>> d1 = np.random.random_integers(1, 6, 1000)>>> d2 = np.random.random_integers(1, 6, 1000)>>> dsums = d1 + d2 Display results as a histogram: >>> import matplotlib.pyplot as plt>>> count, bins, ignored = plt.hist(dsums, 11, normed=True)>>> plt.show()
([size])	返回随机的浮点数，在半开区间 [0.0, 1.0)。 To sample $Unif[a, b), b > a$ multiply the output of by(b-a) and add a: (b - a) * random_sample() + a Examples >>> np.random.random_sample()0.47108547995356098>>> type(np.random.random_sample()) >>> np.random.random_sample((5,))array([ 0.30220482, 0.86820401, 0.1654503 , 0.11659149, 0.54323428]) Three-by-two array of random numbers from [-5, 0): >>> 5 * np.random.random_sample((3, 2)) - 5array([[-3.99149989, -0.52338984], [-2.99091858, -0.79479508], [-1.23204345, -1.75224494]])
([size])	返回随机的浮点数，在半开区间 [0.0, 1.0)。（官网例子与random_sample完全一样）
([size])	返回随机的浮点数，在半开区间 [0.0, 1.0)。（官网例子与random_sample完全一样）
([size])	返回随机的浮点数，在半开区间 [0.0, 1.0)。（官网例子与random_sample完全一样）
(a[, size, replace, p])	生成一个随机样本，从一个给定的一维数组 Examples Generate a uniform random sample from np.arange(5) of size 3: >>> np.random.choice(5, 3)array([0, 3, 4])>>> #This is equivalent to np.random.randint(0,5,3) Generate a non-uniform random sample from np.arange(5) of size 3: >>> np.random.choice(5, 3, p=[0.1, 0, 0.3, 0.6, 0])array([3, 3, 0]) Generate a uniform random sample from np.arange(5) of size 3 without replacement: >>> np.random.choice(5, 3, replace=False)array([3,1,0])>>> #This is equivalent to np.random.permutation(np.arange(5))[:3] Generate a non-uniform random sample from np.arange(5) of size 3 without replacement: >>> np.random.choice(5, 3, replace=False, p=[0.1, 0, 0.3, 0.6, 0])array([2, 3, 0]) Any of the above can be repeated with an arbitrary array-like instead of just integers. For instance: >>> aa_milne_arr = ['pooh', 'rabbit', 'piglet', 'Christopher']>>> np.random.choice(aa_milne_arr, 5, p=[0.5, 0.1, 0.1, 0.3])array(['pooh', 'pooh', 'pooh', 'Christopher', 'piglet'], dtype='\|S11')
(length)	返回随机字节。 >>> np.random.bytes(10)' eh\x85\x022SZ\xbf\xa4' #random

排列

(x)

现场修改序列，改变自身内容。（类似洗牌，打乱顺序）

>>> arr = np.arange(10)>>> np.random.shuffle(arr)>>> arr[1 7 5 2 9 4 3 6 0 8]

This function only shuffles the array along the first index of a multi-dimensional array:

>>> arr = np.arange(9).reshape((3, 3))>>> np.random.shuffle(arr)>>> arrarray([[3, 4, 5],       [6, 7, 8],       [0, 1, 2]])

(x)

返回一个随机排列

>>> np.random.permutation(10)array([1, 7, 4, 3, 0, 9, 2, 5, 8, 6])

>>> np.random.permutation([1, 4, 9, 12, 15])array([15,  1,  9,  4, 12])

>>> arr = np.arange(9).reshape((3, 3))>>> np.random.permutation(arr)array([[6, 7, 8],       [0, 1, 2],       [3, 4, 5]])

分布

(a, b[, size])	贝塔分布样本，在 [0, 1]内。
(n, p[, size])	二项分布的样本。
(df[, size])	卡方分布样本。
(alpha[, size])	狄利克雷分布样本。
([scale, size])	指数分布
(dfnum, dfden[, size])	F分布样本。
(shape[, scale, size])	伽马分布
(p[, size])	几何分布
([loc, scale, size])	耿贝尔分布。
(ngood, nbad, nsample[, size])	超几何分布样本。
([loc, scale, size])	拉普拉斯或双指数分布样本
([loc, scale, size])	Logistic分布样本
([mean, sigma, size])	对数正态分布
(p[, size])	对数级数分布。
(n, pvals[, size])	多项分布
(mean, cov[, size])	多元正态分布。 >>> mean = [0,0]>>> cov = [[1,0],[0,100]] # diagonal covariance, points lie on x or y-axis >>> import matplotlib.pyplot as plt>>> x, y = np.random.multivariate_normal(mean, cov, 5000).T>>> plt.plot(x, y, 'x'); plt.axis('equal'); plt.show()
(n, p[, size])	负二项分布
(df, nonc[, size])	非中心卡方分布
(dfnum, dfden, nonc[, size])	非中心F分布
([loc, scale, size])	正态(高斯)分布 Notes The probability density for the Gaussian distribution is $p(x) = \frac{1}{\sqrt{ 2 \pi \sigma^2 }} e^{ - \frac{ (x - \mu)^2 } {2 \sigma^2} },$ where $\mu$ is the mean and $\sigma$ the standard deviation. The square of the standard deviation, $\sigma^2$ , is called the variance. The function has its peak at the mean, and its “spread” increases with the standard deviation (the function reaches 0.607 times its maximum at $x + \sigma$ and $x - \sigma$ ). Examples Draw samples from the distribution: >>> mu, sigma = 0, 0.1 # mean and standard deviation>>> s = np.random.normal(mu, sigma, 1000) Verify the mean and the variance: >>> abs(mu - np.mean(s)) < 0.01True>>> abs(sigma - np.std(s, ddof=1)) < 0.01True Display the histogram of the samples, along with the probability density function: >>> import matplotlib.pyplot as plt>>> count, bins, ignored = plt.hist(s, 30, normed=True)>>> plt.plot(bins, 1/(sigma * np.sqrt(2 * np.pi)) ... np.exp( - (bins - mu)2 / (2 sigma**2) ),... linewidth=2, color='r')>>> plt.show()
(a[, size])	帕累托（Lomax）分布
([lam, size])	泊松分布
(a[, size])	Draws samples in [0, 1] from a power distribution with positive exponent a - 1.
([scale, size])	Rayleigh 分布
([size])	标准柯西分布
([size])	标准的指数分布
(shape[, size])	标准伽马分布
([size])	标准正态分布 (mean=0, stdev=1).
(df[, size])	Standard Student’s t distribution with df degrees of freedom.
(left, mode, right[, size])	三角形分布
([low, high, size])	均匀分布
(mu, kappa[, size])	von Mises分布
(mean, scale[, size])	瓦尔德（逆高斯）分布
(a[, size])	Weibull 分布
(a[, size])	齐普夫分布

随机数生成器

	Container for the Mersenne Twister pseudo-random number generator.
([seed])	Seed the generator.
()	Return a tuple representing the internal state of the generator.
(state)	Set the internal state of the generator from a tuple.

本文转自罗兵博客园博客，原文链接：http://www.cnblogs.com/hhh5460/p/4324967.html

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