For the initial distributions, initialize the random stream:
savedSeed = sum(100*clock);
RandStream.setDefaultStream(RandStream(’mt19937ar’,’seed’,savedSeed));
defaultStream = RandStream.getDefaultStream;
savedState = defaultStream.State;
save(’RandInit’, ’savedSeed’, ’savedState’);

To re-generate the same distributions again later:
load RandInit.mat
RandStream.setDefaultStream(RandStream(’mt19937ar’,’seed’,savedSeed));
defaultStream = RandStream.getDefaultStream;
defaultStream.State = savedState;

I don’t think I could have worked this out without the benefit of the descriptions and examples shown in the two parts of “New Ways With Random Numbers”.
Thanks,
Joe

You created defaultStream by calling getDefaultStream. But even though you named it “defaultStream” doesn’t mean that someone can’t change the default stream out from under you. Your defaultStream will remain a valid stream, but not necessarily the default stream. I suspect that you ran code (a doc example?) that had something like “rand(’state’,0)” in it. That will change the default stream so that your defaultStream will no longer be the thing that the rand function uses.

Yes, the help says that the seed must be an integer. But over the years MATLAB users have grown accustomed to typing sum(100*clock), and there didn’t seem to be any point in requiring anyone to now start typing round(sum(100*clock)). If you do what the help says, you’ll be fine. But if you deviate slightly because of historical reasons, you’ll get something sensible (and consistent with behavior in the older syntax).

Later, I try to repeat one of the simulations using:
%commands to restore the random number stream state from the saved mat file
load RandState.mat
defaultStream.State = savedState;
%size distribution
Wmean = [2.65 2.75 2.85];
Wstd = [0.05 0.05 0.05];
W = repmat(Wmean,1000,1) +…
repmat(Wstd,1000,1).*randn(1000,size(Wmean,2));

But I do not get the same W distributions. What am I doing wrong?

Also, note that the help for RandStream says that the Seed must be an integer. But sum(100*clock) is not an integer.
Thanks,
Joe

You will get the same answers either way, assuming you start at the same point in the RNG. No difference at all.

–loren

A) x1 = [rand(1) ; rand(1) ; rand(1)];

B) x2 = rand(3,1);

Is there any difference between the following two cases?

A) x1 = [rand(1) ; rand(2) ; rand(3)];

B) x2 = rand(3,1);

In other words, is the statistical distributions of the random numbers is different when you generate them all at once using rand(m,n) or generate them one after another using rand(n) but for m*n times.