gnuplot-beta

how to set a random seed

[Mojca M. <moj...@gm...>]

Dear list,

I'm not sure how I could reset random seed. I have found:

> help rand
 `rand(0)`  returns a pseudo random number in the interval [0:1] generated
            from the current value of two internal 32-bit seeds.
 `rand(-1)` resets both seeds to a standard value.
 `rand(x)`  for x>0 sets both seeds to a value based on the value of x.
 `rand({x,y})` for x>0 sets seed1 to x and seed2 to y.

but I get

gnuplot> rand(42)
         ^
         invalid command

I can use "plot rand(42),rand(0)", but I would like to avoid plotting
anything at all, I just need to reset the seed (I'm using version
control and it is nasty that files change all the time without any
reason).

Thanks,
    Mojca

Re: how to set a random seed

[Daniel J S. <dan...@ie...>]

Mojca,

Gnuplot only has a small set of commands and doesn't access functions 
that way.  Try

print rand(42)

Dan


On 02/10/2011 11:24 AM, Mojca Miklavec wrote:
> Dear list,
>
> I'm not sure how I could reset random seed. I have found:
>
>> help rand
>   `rand(0)`  returns a pseudo random number in the interval [0:1] generated
>              from the current value of two internal 32-bit seeds.
>   `rand(-1)` resets both seeds to a standard value.
>   `rand(x)`  for x>0 sets both seeds to a value based on the value of x.
>   `rand({x,y})` for x>0 sets seed1 to x and seed2 to y.
>
> but I get
>
> gnuplot>  rand(42)
>           ^
>           invalid command
>
> I can use "plot rand(42),rand(0)", but I would like to avoid plotting
> anything at all, I just need to reset the seed (I'm using version
> control and it is nasty that files change all the time without any
> reason).
>
> Thanks,
>      Mojca
>
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-- 

Dan Sebald
email: daniel(DOT)sebald(AT)ieee(DOT)org
URL: http://www(DOT)dansebald(DOT)com

Re: how to set a random seed

[Mojca M. <moj...@gm...>]

On Thu, Feb 10, 2011 at 18:45, Daniel J Sebald wrote:
> Mojca,
>
> Gnuplot only has a small set of commands and doesn't access functions
> that way.  Try
>
> print rand(42)

Dear Daniel,

Thanks a lot for the hint. This works OK, as well as somebody else's idea to use
   foo = rand(42)

Not that many people care about setting random seed, but it might make
sense to add a tiny note next to "help rand" about the usage (for
those of us who are not so familiar with syntactic rules).

Thanks,
   Mojca

Re: how to set a random seed

[Daniel J S. <dan...@ie...>]

On 02/10/2011 02:48 PM, Mojca Miklavec wrote:
> On Thu, Feb 10, 2011 at 18:45, Daniel J Sebald wrote:
>> Mojca,
>>
>> Gnuplot only has a small set of commands and doesn't access functions
>> that way.  Try
>>
>> print rand(42)
>
> Dear Daniel,
>
> Thanks a lot for the hint. This works OK, as well as somebody else's idea to use
>     foo = rand(42)
>
> Not that many people care about setting random seed,

Probably plenty of people care; for reasons of repeatable simulations 
being one example.


> but it might make
> sense to add a tiny note next to "help rand" about the usage (for
> those of us who are not so familiar with syntactic rules).

I hear you Mojca.  However there are a lot of functions that fall in the 
same category as rand().  Many other functions have the word "function" 
in the documentation, whereas rand documentation does not.  Perhaps that 
could be specified.

I did create a patch a while back for rand that I thought was a 
worthwhile improvement for controlling the seed(s).  Perhaps I can 
update that and place it in sourceforge.

Dan