rand (MATLAB Function Reference)

rand	Examples See Also

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.

Remarks

MATLAB 5 uses a new multiseed random number generator that can generate all the floating-point numbers in the closed interval

Theoretically, it can generate over

values before repeating itself. MATLAB 4 used random number generators with a single seed. rand('seed',0)and rand('seed',j) use the MATLAB 4 generator. rand('seed') returns the current seed of the MATLAB 4 uniform generator. rand('state',j) and rand('state',s) use the MATLAB 5 generator.

Examples

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