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1、Matlab 各种随机数设置 randn（伪随机正态分布数）（伪随机正态分布数） Normally distributed pseudorandom numbers Syntax r = randn(n) randn(m,n) randn(m,n) randn(m,n,p,.) randn(m,n,p,.) randn(size(A) r = randn(., double) r = randn(., single)Description r = randn(n) returns an n-by-n matrix containing pseudorandom values drawn fro
2、m the standard normal distribution. randn(m,n) or randn(m,n) returns an m-by-n matrix. randn(m,n,p,.) or randn(m,n,p,.) returns an m-by-n-by-p-by-. array. randn returns a scalar. randn(size(A) returns an array the same size as A. r = randn(., double) or r = randn(., single) returns an array of norma
3、l values of the specified class. Note The size inputs m, n, p, . should be nonnegative integers. Negative integers are treated as 0. The sequence of numbers produced by randn is determined by the internal state of the uniform pseudorandom number generator that underlies rand, randi, and randn. randn
4、 uses one or more uniform values from that default stream to generate each normal value. Control the default stream using its properties and methods.Note In versions of MATLAB prior to 7.7 (R2008b), you controlled the internal state of the random number stream used by randn by calling randn directly
5、 with the seed or state keywords. Examples Generate values from a normal distribution with mean 1 and standard deviation 2. r = 1 + 2.*randn(100,1); Generate values from a bivariate normal distribution with specified mean vector and covariance matrix. mu = 1 2; Sigma = 1 .5; .5 2; R = chol(Sigma); z
6、 = repmat(mu,100,1) + randn(100,2)*R; Replace the default stream at MATLAB startup, using a stream whose seed is based on clock, so that randn will return different values in different MATLAB sessions. It is usually not desirable to do this more than once per MATLAB session. RandStream.setDefaultStr
7、eam . (RandStream(mt19937ar,seed,sum(100*clock); randn(1,5) Save the current state of the default stream, generate 5 values, restore the state, and repeat the sequence.defaultStream = RandStream.getDefaultStream; savedState = defaultStream.State; z1 = randn(1,5) defaultStream.State = savedState; z2
8、= randn(1,5) % contains exactly the same values as z1Normrnd （随机正态分布数）（随机正态分布数） Normal random numbers Syntax R = normrnd(mu,sigma) R = normrnd(mu,sigma,m,n,.) R = normrnd(mu,sigma,m,n,.)Description R = normrnd(mu,sigma) generates random numbers from the normal distribution with mean parameter mu and
9、 standard deviation parameter sigma. mu and sigma can be vectors, matrices, or multidimensional arrays that have the same size, which is also the size of R. A scalar input for mu or sigma is expanded to a constant array with the same dimensions as the other input. R = normrnd(mu,sigma,m,n,.) or R =
10、normrnd(mu,sigma,m,n,.) generates an m-by-n-by-. array. The mu, sigma parameters can each be scalars or arrays of the same size as R.Examples n1 = normrnd(1:6,1./(1:6) n1 =2.1650 2.3134 3.0250 4.0879 4.8607 6.2827n2 = normrnd(0,1,1 5) n2 =0.0591 1.7971 0.2641 0.8717 -1.4462n3 = normrnd(1 2 3;4 5 6,0
11、.1,2,3) n3 =0.9299 1.9361 2.9640 4.1246 5.0577 5.9864randperm (RandStream) （区域内的所有整数的随机分布）（区域内的所有整数的随机分布） Random permutation randperm(s,n)Description randperm(s,n) generates a random permutation of the integers from 1 to n. For example, randperm(s,6) might be 2 4 5 6 1 3. randperm(s,n) uses random v
12、alues drawn from the random number stream s.betarnd （贝塔分布）（贝塔分布） 贝塔分布是一个作为伯努利分布和二项式分布的共轭先验分布的密度函数 Syntax R = betarnd(A,B) R = betarnd(A,B,m,n,.) R = betarnd(A,B,m,n,.)Description R = betarnd(A,B) generates random numbers from the beta distribution with parameters specified by A and B. A and B can be
13、 vectors, matrices, or multidimensional arrays that have the same size, which is also the size of R. A scalar input for A or B is expanded to a constant array with the same dimensions as the other input.R = betarnd(A,B,m,n,.) or R = betarnd(A,B,m,n,.) generates an m-by-n-by-. array containing random
14、 numbers from the beta distribution with parameters A and B. A and B can each be scalars or arrays of the same size as R.Examples a = 1 1;2 2; b = 1 2;1 2; r = betarnd(a,b) r =0.6987 0.61390.9102 0.8067r = betarnd(10,10,1 5) r =0.5974 0.4777 0.5538 0.5465 0.6327r = betarnd(4,2,2,3) r =0.3943 0.6101
15、0.5768 0.5990 0.2760 0.5474Binornd （二项式分布）（二项式分布） 二项分布（binomial distribution）就是对这类只具有两种互斥结果的离散型随机事件的规 律性进行描述的一种概率分布。Syntax R = binornd(N,P) R = binornd(N,P,m,n,.) R = binornd(N,P,m,n,.)Description R = binornd(N,P) generates random numbers from the binomial distribution with parameters specified by t
16、he number of trials, N, and probability of success for each trial, P. N and P can be vectors, matrices, or multidimensional arrays that have the same size, which is also the size of R. A scalar input for N or P is expanded to a constant array with the same dimensions as the other input.R = binornd(N,P,m,n,.) or R = binornd(N,P,m,n,.)
