okay now I get it.
but then
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
int i;
do
{
i = 5 * (rand5() - 1) + rand5(); // i is now uniformly random
between 1 and 25
} while(i > 7);
return i;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
should be fine. isn't it??
On Sep 18, 6:06 pm, Dave <dave_and_da...@juno.com> wrote:
> What is wrong with using i = rand5() + rand5() instead of i = 5 * rand5
> () + rand5() is that the former is not uniformly distributed between 1
> and 10, as claimed. First, 1 never occurs. 2 occurs 1 out of 25 times,
> 3 occurs 2 out of 25, etc. (Think of rolling two ordinary dice.)
>
> Dave
>
> On Sep 18, 6:19 am, eSKay <catchyouraak...@gmail.com> wrote:
>
> > one of the solutions given
> > athttp://stackoverflow.com/questions/137783/given-a-function-which-prod...
> > is:
>
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > int i;
> > do
> > {
> > i = 5 * (rand5() - 1) + rand5(); // i is now uniformly random
> > between 1 and 25} while(i > 21);
>
> > // i is now uniformly random between 1 and 21
> > return i % 7 + 1; // result is now uniformly random between 1 and 7
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> > Why do we need to go for all this trouble??
>
> > Why not:
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > int i;
> > do
> > {
> > i = rand5() + rand5(); // i is now uniformly random between 1 and
> > 10} while(i > 7);
>
> > // i is now uniformly random between 1 and 7
> > return i;
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > Whats wrong with it??
>
> > On Sep 9, 12:34 am, Ramaswamy R <ramaswam...@gmail.com> wrote:
>
> > > Generate the random number 7 times. Sum them all and divide by 5.
> > > Theoritically it should be evenly distributed over 1-7. But owing to
> > > random
> > > number generators characteristics the sum of rand(5) called 7 times may
> > > not
> > > be perfectly evenly distributed over 1-7.
> > > A nice discussion on some neat options is available here
> > > -http://stackoverflow.com/questions/137783/given-a-function-which-prod...
>
> > > Rejection technique is pretty standard for this and yet simple.
>
> > > On Mon, Sep 7, 2009 at 8:56 AM, ankur aggarwal
> > > <ankur.mast....@gmail.com>wrote:
>
> > > > Given a random number generator that generates numbers in the range 1
> > > > to
> > > > 5, how can u create a random number generator to generate numbers in the
> > > > range 1 to 7. (remember that the generated random numbers should follow
> > > > a
> > > > uniform distribution in the corresponding range)
>
> > > --
> > > Yesterday is History.
> > > Tomorrow is a Mystery.
> > > Today is a Gift! That is why it is called the Present :).
>
> > >http://sites.google.com/site/ramaswamyr-Hide quoted text -
>
> > - Show quoted text -
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