Explain this one line of code

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Aftab Ahmed Khan
Aftab Ahmed Khan 2014-7-7
评论： Star Strider 2014-7-7
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

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采纳的回答

Star Strider
Star Strider 2014-7-7
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.
  2 个评论
Aftab Ahmed Khan
Aftab Ahmed Khan 2014-7-7
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
Star Strider 2014-7-7
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).

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更多回答（2 个）

Ben11
Ben11 2014-7-7
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.
Shashank Prasanna
编辑：Shashank Prasanna 2014-7-7
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.

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