rand (MATLAB Functions)

Uniformly distributed random numbers and arrays

Syntax

Y = rand(n)
Y = rand(m,n)
Y = rand([m n])
Y = rand(m,n,p,...)
Y = rand([m n p...])
Y = rand(size(A))
rand
s = rand('state')

Description

The rand function generates arrays of random numbers whose elements are uniformly distributed in the interval (0,1).

Y = rand(n) returns an n-by-n matrix of random entries. An error message appears if n is not a scalar.

Y = rand(m,n) or Y = rand([m n]) returns an m-by-n matrix of random entries.

Y = rand(m,n,p,...) or Y = rand([m n p...]) generates random arrays.

Y = rand(size(A)) returns an array of random entries that is the same size as A.

rand, by itself, returns a scalar whose value changes each time it's referenced.

s = rand('state') returns a 35-element vector containing the current state of the uniform generator. To change the state of the generator:

rand('state',s)
Resets the state to s.

rand('state',0)
Resets the generator to its initial state.

rand('state',j)
For integer j, resets the generator to its j-th state.

rand('state',sum(100*clock))
Resets it to a different state each time.

`rand('state',s)`	Resets the state to `s`.
`rand('state',0)`	Resets the generator to its initial state.
`rand('state',j)`	For integer `j`, resets the generator to its `j`-th state.
`rand('state',sum(100*clock))`	Resets it to a different state each time.

Examples

Example 1. R = rand(3,4) may produce

 R =
    0.2190    0.6793    0.5194    0.0535
    0.0470    0.9347    0.8310    0.5297
    0.6789    0.3835    0.0346    0.6711

This code makes a random choice between two equally probable alternatives.

 if rand < .5
    'heads'
 else
    'tails'
 end

Example 2. Generate a uniform distribution of random numbers on a specified interval [a,b]. To do this, multiply the output of rand by (b-a) then add a. For example, to generate a 5-by-5 array of uniformly distributed random numbers on the interval [10,50]

a = 10; b = 50;
x = a + (b-a) * rand(5)
x =

   18.1106   10.6110   26.7460   43.5247   30.1125
   17.9489   39.8714   43.8489   10.7856   38.3789
   34.1517   27.8039   31.0061   37.2511   27.1557
   20.8875   47.2726   18.1059   25.1792   22.1847
   17.9526   28.6398   36.8855   43.2718   17.5861

See Also

randn, randperm, sprand, sprandn

qz randn