Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From |
Sergiy Radyakin <serjradyakin@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: sequence of random values is repeated as I re-run code |

Date |
Fri, 4 Feb 2011 09:29:20 -0500 |

On Fri, Feb 4, 2011 at 7:07 AM, Prado De Castro Alfaiate, Jorge <jprado@essex.ac.uk> wrote: > Dear statalisters, > > I still could not understand why, but I found out that the same sequence of random values is created when I re-run my code. > > Each time a random value is created Stata is supposed to get that random number by using a complicated function of time and date (with high precision), leading to a near-random number, right? > > But then I do not understand how the same random numbers may come out again... > Hello Jorge, I guess you have discovered the fundamental truth about random number generation in Stata (and all the other packages and programming languages for that matter).The random number generation is implemented with a pseudo-random number generator, which repeats the same sequence over and over again, and that sequence appears to be random to the naked eye, but it is of course not. For practical matters the following properties are particularly notable: it has a repetition cycle, and a sophisticated guesser equipped with a calculator, good memory and a prior knowledge of the previous few observations of the rnds can predict with 100% certainty what's coming next. Being able to reproduce the same sequence of random numbers is often important during software development for testing and making sure the software behaves properly. For true random numbers, see the -truernd- command recently posted to SSC. http://ideas.repec.org/c/boc/bocode/s457232.html Best regards, Sergiy Radyakin > Anyone knows why this might be happening? > > Best, > > Jorge > > Jorge Prado de Castro Alfaiate > PhD student, > Department of Economics, > University of Essex > email: jprado@essex.ac.uk > > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: sequence of random values is repeated as I re-run code***From:*Nick Cox <n.j.cox@durham.ac.uk>

**References**:**st: sequence of random values is repeated as I re-run code***From:*"Prado De Castro Alfaiate, Jorge" <jprado@essex.ac.uk>

- Prev by Date:
**RE: RE: st: RE: RE: Calculating moving windows over time with conditions** - Next by Date:
**RE: st: RE: RE: Calculating moving windows over time with conditions** - Previous by thread:
**st: RE: sequence of random values is repeated as I re-run code** - Next by thread:
**RE: st: sequence of random values is repeated as I re-run code** - Index(es):