Explain this one line of code

Hi,

Can anyone explain to me this one line, what actually this one line do ?

rand('state',sum(100*clock));                   % resetting of the random table

Answer 1

[Star Strider]

It’s an obsolete way of resetting the seed of the random number generator. See the documentation on Replace Discouraged Syntaxes of rand and randn for details.

[Aftab Ahmed Khan]

Hi Strider,

In short, does it mean that everytime i use the rand function, it will generate a different set of numbers? Am i right ?

[Star Strider]

Yes. It’s set up in that statement to set the seed based on the current time (the sum of the elements in the six-element date vector returned by clock).

Answer 2

[Ben11]

I think this ensures that random numbers generated from different calls are all different since you use the current date/time in your call. You might want to take a look at this:

http://www.mathworks.com/help/matlab/math/updating-your-random-number-generator-syntax.html

in which The Mathworks discourages using this syntax and proposes alternatives.

Answer 3

[Shashank Prasanna]

Aftab, Random number generators are really pseudorandom (deterministic). This means for a given "seed" you can consistently regenerate the same sequence. This is useful if you want to re-run your experiment or perform multiple experiments on the same random stream.

In short, yes, using clock to reset the seed with generate a different stream each time since the clock is different each moment. However the recommended way to change the seed is to use the RNG function:

rng('shuffle')

http://www.mathworks.com/help/matlab/ref/rng.html

Also all the link provided by SS and Ben are relevant.