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

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

Subject |
st: RE: Re: Compositional data |

Date |
Wed, 5 Mar 2008 20:41:20 -0000 |

For more details on the Aitchison book, which sells under a slightly different title, see http://www.blackburnpress.com/stanofcoda.html A standard graphic for your 3-D response data is variously known as a triangle triangular trilinear triaxial trinomial ternary three-element mixture or barycentric plot, chart, graph or diagram. A Stata implementation is in -triplot- from SSC. Stata graphics freaks might note that it is really a scatter plot in disguise. A project of mine for 2008, already started, is to publish Stata programs for alternatives to such plots, all using some kind of transformation, including some suggested by Aitchison. Nick n.j.cox@durham.ac.uk Verkuilen, Jay >>I would like to estimate the following model: i have n firms, each firm has a bundle of 3 products, characterized by the different resource allocation for each product, measured in % which sums up to 100%. That is, e.g. firm 1 has 20% of production devoted to product 1, 30% to product 2, etc., 100% in total. I would like to explain the resource allocation choice by a firm. Thus, the dependent variable is actually 3 variables, which are continuous variables (% of resources) and are interdependent. Which econometric model should I use and how to handle this in stata? Thanks very much in advance, Regards, Elena<< As Maarten noted, you have compositional data. Might I suggest looking at the book by John Aitchison, Compositional Data Analysis (2003)? Also Fry, J.M., Fry, T.R.L. and K.R. McLaren, (1996), "The Stochastic Specification of Demand Share Equations: Restricting Budget Shares to the Unit Simplex", Journal of Econometrics, 73, 377-385. The Dirichlet distribution is convenient but has a very restrictive covariance structure, because it is fully determined by its marginals. * * 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**:**st: RE: RE: Re: Compositional data***From:*"Verkuilen, Jay" <JVerkuilen@gc.cuny.edu>

**References**:**st: From: "E. Golovko" <E.Golovko@uvt.nl>***From:*owner-statalist@hsphsun2.harvard.edu

**st: Re: Compositional data***From:*"Verkuilen, Jay" <JVerkuilen@gc.cuny.edu>

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