randperm MATLAB : Random Number Generation in Matlab Programming

There are four basic fundamental random number functions available in MATLAB: rand, randi, randn, and randperm.

The rand function returns real numbers between 0 and 1 that are drawn from a uniform distribution in MATLAB. For example,

r1 = rand(1000,1);

r1 is a 1000-by-1 column vector containing real floating-point numbers drawn from a uniform distribution. All the values in r1 are in the open interval (0, 1). Histogram of these values is show roughly flat nature, which indicates a fairly uniform sampling of numbers.

The randi function gives back double integer values drawn from a discrete uniform distribution.

r2 = randi(10,1000,1);

r2 is a 1000-by-1 column vector containing integer values drawn from a discrete uniform distribution whose range is 1,2,...,10. A histogram of these values is also turnout to be roughly flat in nature, which indicates a fairly uniform sampling of integers between 1 and 10.

The randn function gives arrays of real floating-point numbers that are made from a standard normal distribution. For example,

r3 = randn(1000,1);

r3 written above is a 1000-by-1 column vector containing numbers drawn from a standard normal distribution. Histogram of r3 comes like a roughly normal distribution whose mean is 0 and standard deviation is 1.

The randperm function can be used to create arrays of random integer values that have no repeated values. For example,

r4 = randperm(15,5);

r4 written above is a 1-by-5 array containing randomly selected integer values on the closed interval, [1, 15]. Unlike randi, which can give an array containing repeated values, the array returned by randperm has no repeated values.

Successive calls to any of above functions return different results. This behavior is helpful for creating several different arrays of random values.