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Matlab 各种随机数设置

randn (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 from 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 normal 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 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 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 = 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.setDefaultStream ...

(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 = randn(1,5) % contains exactly the same values as z1

Normrnd (随机正态分布数)

Normal random numbers

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