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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

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

Subject |
RE: st: RE: model for fractional data with panel data |

Date |
Wed, 7 Nov 2007 13:51:02 -0000 |

Quite so. The beta-distribution can indeed be U-shaped. Some people would call that shape bimodal. Others define a mode as a peak with a tail on either side, so that on such a stricter definition we have in Maarten's case two half-modes. (That doesn't make it unimodal!) Maarten buis --- Maarten buis <maartenbuis@yahoo.co.uk> wrote: > You can see graphs of such bimodel beta distribution in the example > below. Actually that code contained a minor error in the calculation of the constant. It does not change the shape, so the message from these graphs doesn't change, but the correct code is below: *-------------------- begin example ---------------- /*conventional parameterization*/ twoway function y = betaden(.5, .7, x) /*alternative parameterization*/ local phi = 1.5 local mu = .5 local constant = exp(lngamma(`phi'))/ /// (exp(lngamma(`mu'*`phi'))*exp(lngamma((1-`mu')*`phi'))) twoway function y = `constant'* /// x^(`mu'*`phi'-1)* /// (1-x)^((1-`mu')*`phi'-1) *-------------------- end example ------------------ * * 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: RE: model for fractional data with panel data***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**References**:**RE: st: RE: model for fractional data with panel data***From:*Maarten buis <maartenbuis@yahoo.co.uk>

**RE: st: RE: model for fractional data with panel data***From:*Maarten buis <maartenbuis@yahoo.co.uk>

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