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From |
Steve Samuels <sjsamuels@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Generate a random double between -1 and 1 |

Date |
Sun, 2 Sep 2012 16:50:34 -0400 |

Your statement that > "...multiplying 2 * runiform() excludes half the > possible values between -1 and 1." is incorrect, as the limits of -1 + 2*runiform() are -1 + 2*0 = -1, and -1 +2*1 = +1. Steve On Sep 2, 2012, at 3:45 PM, Nick Cox wrote: See <http://blog.stata.com/2012/08/29/using-statas-random-number-generators-part-3-drawing-with-replacement/> and prequels. Nick On Sun, Sep 2, 2012 at 8:26 PM, Aaron Kirkman <ak5791@gmail.com> wrote: > I have a situation where I need to generate random real numbers > between -1 and 1, and I'm wondering if there is a better way to > accomplish this. Right now, I use this: > > clear > set obs 100000000 > gen double eps = -1 + 2 * runiform() > summ eps > > While this is probably acceptable, as the theoretical mean is 0, it's > problematic because multiplying 2 * runiform() excludes half the > possible values between -1 and 1. Is there a built-in way to do this > in a way that won't exclude values, or is this method sufficient? In > practice, I may generate as few as 30 random numbers and as many as > 100,000,000 (if that's relevant). * * 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: Generate a random double between -1 and 1***From:*Aaron Kirkman <ak5791@gmail.com>

**References**:**st: Generate a random double between -1 and 1***From:*Aaron Kirkman <ak5791@gmail.com>

**Re: st: Generate a random double between -1 and 1***From:*Nick Cox <njcoxstata@gmail.com>

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