All the random number functions,rand,randn,randi, andrandperm, draw values from a shared random number generator. Every time you start MATLAB, the generator resets itself to the same state. Therefore, a command such asrand(2,2)returns the same result any time you execute it immediately following startup. Also, any script or function that calls the random number functions returns the same result whenever you restart.

One way to get different random numbers is to initialize the generator using a different seed every time. Doing so ensures that you don’t repeat results from a previous session.

Execute therng('shuffle')command once in your MATLAB session before calling any of the random number functions.

rng('shuffle')

You can execute this command in a MATLAB Command Window, or you can add it to your startup file, which is a special script that MATLAB executes every time you restart.

Now, execute a random number command.

A = rand(2,2);

每一次你叫rng('shuffle'), it reseeds the generator using a different seed based on the current time.

Alternatively, specify different seeds explicitly in different MATLAB sessions. For example, generate random numbers in one MATLAB session.

rng(1); A = rand(2,2);

Use different seeds to generate random numbers in another MATLAB session.

rng(2); B = rand(2,2);

ArraysAandBare different because the generator is initialized with a different seed before each call to therandfunction.

To generate multiple independent streams that are guaranteed to not overlap, and for which tests that demonstrate independence of the values between streams have been carried out, you can useRandStream.create. For more information about generating multiple streams, seeMultiple Streams.