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From |
"Daniel Waxman" <dan@amplecat.com> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: simulated data for logistic regression... remedial algebra help? |

Date |
Mon, 19 Nov 2007 22:37:22 -0500 |

*Success* Steven, Thank you very much for the help. Quadratic formula ... brings back memories. There was a wicked exponentiation problem that took a few hours to figure out (beware of how Stata evaluates the exponentiation of a negative number... e.g. -2^2 evaluates to -4) Anyway, here is the result: **** clear set obs 1000 local odds=2 local proportion_positive= .10 local mortality = .05 gen test=uniform()<`proportion_positive' local k1=`mortality'/(1-`proportion_positive') local k2=(`proportion_positive'/(1-`proportion_positive')) di `k1' di `k2' local a=`k2' local b=(-2)*`k2'-`k1'-1 local c=2*`k1' gen probability_positive = ((-`b') - (sqrt((`b')^2-(4*`a'*`c'))))/(2*`a') gen probability_negative = (`k1')-((`k2')*probability_positive) gen died=uniform() < cond(test==0,probability_negative,probability_positive) logistic died test ****************** Thanks much! Dan -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steven Joel Hirsch Samuels Sent: Monday, November 19, 2007 12:07 PM To: statalist@hsphsun2.harvard.edu Subject: Re: st: RE: simulated data for logistic regression... remedial algebra help? > >> On Nov 19, 2007, at 9:49 AM, Steven Joel Hirsch Samuels wrote: >>> > p1 = (p -(1 -w)p2)/w =B (you left out the 1-w term in your k2 > coefficient) >>> No you didn't, Daniel. Sorry. -Steven * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.16.0/1139 - Release Date: 11/19/2007 12:35 PM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.16.0/1139 - Release Date: 11/19/2007 12:35 PM * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: simulated data for logistic regression... remedial algebra help?***From:*Richard Williams <Richard.A.Williams.5@ND.edu>

**References**:**st: simulated data for logistic regression... remedial algebra help?***From:*"Daniel Waxman" <dan@amplecat.com>

**st: RE: simulated data for logistic regression... remedial algebra help?***From:*"Daniel Waxman" <dan@amplecat.com>

**Re: st: RE: simulated data for logistic regression... remedial algebra help?***From:*Steven Joel Hirsch Samuels <sjhsamuels@earthlink.net>

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