[R] Help creating the IBM Randu function

[Martin Møller Skarbiniks Pedersen]

Dear all,

  I am trying to learn functions in R and 3D plotting so I decided to try
to plot
the famous bad PRNG Randu from IBM(1).
   However something is not correct in the function I have created.
   First I define the function RANDU like this:

> RANDU <-  function(num) { return (65539*num)%%(2^31) }

and test that it works for a seed of 1:
> RANDU(1)
[1] 65539

but if I want the next value in the sequence I get this number.
> (65539*65539)%%(2^31)
[1] 393225

However using the RANDU function twice doesn't give the same result as
above.

> RANDU(RANDU(1))
[1] 4295360521

I expect these two values to be the same but that is not the case.
393225 should be the correct.

I guess it might be something with local vs. global environment ?!

Please advise and thanks.

Regards
Martin M. S. Pedersen

(1) https://en.wikipedia.org/wiki/RANDU

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