Simulink random number repeats every time the simulation runs

Hi,

In Simulink, using RTW, I need to generate a random number in the [1,3] range and i need the number to be different every simulation. Is there any comand to generate a random seed and not get the same seed every simulation that does not involve using extrinsic functions?

Thanks in advance!

Answer 1

[Jan]

Seed the random number generator in the InitFcn:

RandStream.setDefaultStream( ...
     RandStream('mt19937ar', 'seed', sum(100 * clock))

Actually it should be enough to do this once in a Matlab session. Therefore I assume a PERSISTENT variable might be helpful:

persistent Seeded
if isempty(Seeded)
  ... the above seeding code
  Seeded = true;
end

Answer 2

[Paulo Silva]

Go to File, Model Properties, callbacks, InitFcn

n=randi([1 3])

if you don't wan't to have repeated n values, first check if n exists in the workspace, if it exist get it's value and generate n values until they are diferent (while (n0==n) generate another n)

if ismember('n',who) %check if there's already one n value in memory
    n0=n; %there's one, save it to n0
    while (n0==n) %get another n diferent from n0
        n=randi([1 3]);
    end
else
    n=randi([1 3]); %there's no n in memory get one
end

The code can fail if there's one n in memory that's not a number, use a variable with a big and/or unique name or add code to handle that situation.