What 0 represents in rand function?

What rand ('state', 0) is represents. i read in the document, it shows that it is generating random number. Not clear about what state and 0 represents. how can i verify it in matlab?

Also it is mentioned old version follows this way of representation. In new version it is changed. if so how i can represent it in current version. will current version still accept the above line?

[SRI]

Hi

Did you try typing this command in matlab,since it outperform no result

[subha]

yes i tried by typing. i got same. thats why to clarify i posted here

Answer 1

[Geoff Hayes]

See this link http://www.mathworks.com/help/matlab/math/updating-your-random-number-generator-syntax.html which discusses the "discouraged" syntaxes of rand, which includes your example of rand('state',0).

From the documentation:

In earlier versions of MATLAB®, you controlled the random number generator used by the rand and randn functions with the 'seed', 'state' or 'twister' inputs...These syntaxes referred to different types of generators, and they will be removed in a future release for the following reasons:

• The terms 'seed' and 'state' are misleading names for the generators.
• All of the former generators except 'twister' are flawed.
• They unnecessarily use different generators for rand and randn.

It goes on to discuss what the intent was behind rand('state',sd), why it was discouraged, and what it should be replaced by.

In your case, the alternative for rand('state',sd) would be rng(sd). It is best to use the recommended alternative as per the note.

You can verify that the original call still does work (though it should be replaced!). In the Command Window type

 rand('state',0)
 A = rand(100,1);
 rand('state',0);
 B = rand(100,1);
 find((A-B)~=0)

Note that A and B will have the same set of randomly generated numbers, so find((A-B)~=0) will be zero.

[subha]

 Thanks for your explanation. could you please explain me the difference between rng(0) and rng('shuffle') with some example. 

 If i use both in one program what will be the effect?

[Geoff Hayes]

Please check out the documentation for rng which states

rng(sd) seeds the random number generator using the nonnegative integer sd so that rand, randi, and randn produce a predictable sequence of numbers.

rng('shuffle') seeds the random number generator based on the current time so that rand, randi, and randn produce a different sequence of numbers after each time you call rng.

Alternate between the two and observe what happens when you call (say)

 randn(5,1)

between each call to rng.

[subha]

When i typed, rng(0)and x= rand(1,5), every time i run, i get same random values. But if i type rng('shuffle') and then x=rand(1,5), it provides different random numbers each time. I understand this from your statement as well as from documents. If i use both, for example rng(0) and rng('shuffle') and then x=rand(1,5), i guess rng('shuffle') overwrites rng(0). it means, i will get different sequence of numbers every time. Am i right?

[Geoff Hayes]

Yes. Because you call rng('shuffle') after rng(0) there will be a different sequence of numbers.