Matlab中的随机函数 (2)

RNG

The sequence of numbers produced by randi is determined by the settings of the uniform random number generator that underlies RAND, RANDN, and randi. randi uses one uniform random value to create each integer random value. Control that shared random number generator using RNG.

randi

Pseudorandom integers from a uniform discrete distribution.

1) randi(IMAX) returns a scalar.

2) R = randi(IMAX,N) returns an N-by-N matrix containing pseudorandom integer values drawn from the discrete uniform distribution on 1:IMAX.

3) randi(IMAX,M,N,P,...) or randi(IMAX,[M,N,P,...]) returns an M-by-N-by-P-by-... array.

4) R = randi([IMIN,IMAX],...) returns an array containing integer values drawn from the discrete uniform distribution on IMIN:IMAX.

5) randi(..., CLASSNAME) returns an array of integer values of class CLASSNAME.

设置随机函数的格式Example 1: Save the settings for the random number generator used by RAND, randi, and RANDN, generate 5 values from randi, restore the settings, and repeat those values.

s = rng

i1 = randi(10,1,5)

rng(s);

i2 = randi(10,1,5) % i2 contains exactly the same values as i1

让每次执行随机结果不一Example 2: Reinitialize the random number generator used by RAND,randi, and RANDN with a seed based on the current time. randi will return different values each time you do this. NOTE: It is usually not necessary to do this more than once per MATLAB session.

rng('shuffle');

randi(10,1,5)

To get unique integer values, sometimes referred to as sampling without replacement,then coming into being.

RANDPERM.

Diag

对角矩阵 eg、 a = [1,2,3] 则： diag(a) = (1 0 0 ;0 2 0;0 0 6);

Triu

上三角矩阵 eg、 a2 = [1,2,3;4,5,6,;7,8,9] 则： diag(a2) = (1 2 3 ;0 5 6;0 0 9); Tril

下三角矩阵 eg、 a3 = a2 则： diag(a) = (1 0 0 ;4 5 0;7 8 9);

Zeros

全零矩阵

Ones

全一矩阵

Eye

单位矩阵