Notice: On March 31, it was **announced** that Statalist is moving from an email list to a **forum**. The old list will shut down on April 23, and its replacement, **statalist.org** is already up and running.

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

From |
Maarten Buis <maartenlbuis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: ZOIB procedure |

Date |
Mon, 19 Sep 2011 15:43:34 +0200 |

On Mon, Sep 19, 2011 at 3:12 PM, Cameron McIntosh wrote: > For proportions, Warton et al. (2011) recommend a logit transformation to achieve linearity. You could then run a linear model in -gllamm-, while allowing cov(e1,e2) and back-transform the predicted values (yhats). You do not have to use -gllamm- for that, use -mvreg- instead. In that case you are using Aitchison's (2003) method. > Exponentiating these should return the geometric mean value of the yhats, and the geometric mean and median are (asymptotically) equivalent. That is not quite correct, you will get the geometric mean if you log transform your dependent variable, and afterwards exponentiate the mean. With the logit transformation the back-transform is fairly meaningless. See the example below: *------------ begin example ---------------- sysuse auto, clear sum price, meanonly gen pprice = (price - r(min) ) /(r(max) - r(min)) gen logit = logit(pprice) gen log = ln(pprice) ameans pprice sum logit, meanonly di invlogit(r(mean)) sum log, meanonly di exp(r(mean)) *------------ end example ---------------- (For more on examples I sent to the Statalist see: http://www.maartenbuis.nl/example_faq ) -- Maarten Aitchison (2003) The Statistical Analysis of Compositional Data. Caldwell, NJ: The Blackburn Press. -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * 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: ZOIB procedure***From:*Prerna S <maruiprerna@gmail.com>

**References**:**st: ZOIB procedure***From:*Prerna S <maruiprerna@gmail.com>

**RE: st: ZOIB procedure***From:*Cameron McIntosh <cnm100@hotmail.com>

**Re: st: ZOIB procedure***From:*Prerna S <maruiprerna@gmail.com>

**RE: st: ZOIB procedure***From:*Cameron McIntosh <cnm100@hotmail.com>

- Prev by Date:
**st: change values in the x-axis** - Next by Date:
**Re: st: String variables over 244 in a dataset with two delimiters** - Previous by thread:
**RE: st: ZOIB procedure** - Next by thread:
**Re: st: ZOIB procedure** - Index(es):