I’ll be giving a shortened version of my Bayesian stable isotope mixing model talk (title and abstract below) at the Albuquerque Chapter of the American Statistical Association (ACASA) annual meeting on Friday, April 29, 2011. I gave two distinct longer versions of this talk recently as part of job interview talks at St. Louis University and the University of New Mexico. I’m looking forward to the meeting to visit with people who I’ve worked with over the last several years, organizing judging events at science fairs, and other events.
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Research, Statistics
In a previous post I discussed this paper and how fun it was to write with Laurel. Here I’m happy to report it’s available electronically (SpringerLink, pdf) and soon in paper.
Laurel K. Goode, Erik B. Erhardt, Louis S. Santiago, Michael F. Allen. Carbon stable isotopic composition of soluble sugars in Tillandsia epiphytes varies in response to shifts in habitat. Oecologia (2010) 163:583–590.
DOI 10.1007/s00442-010-1577-5
Received: 11 March 2009 / Accepted: 25 January 2010 / Published online: 13 February 2010
Research, stable isotopes, Statistics
A few important areas of focus, reflecting what I’m doing and where I’m going. Read more…
MIND, Research, stable isotopes, Statistics
Laurel Goode, Erik Erhardt, Louis Santiago, and Michael Allen.
δ13C of soluble sugars in Tillandsia epiphytes vary in response to shifts in habitat.
Oecologia, Physiological ecology section, 2010.
I met Laurel at SIRFER 2008 where we enjoyed a wide range of stable isotope lectures and lab experience. She first used my software, SISUS, to estimate the proportion of C3 vs CAM photosynthesis of epiphytes. Our work and friendship led to the collaboration where we thought about and developed a model for the environmental factors affecting the phothsynthetic pathways of the species studied. Read more…
stable isotopes, Statistics
The Wishart distribution and especially the inverse-Wishart distribution are the source of some confusion because they occasionally appear with alternative parameterizations. Also, the Wishart distribution can be used to model a covariance matrix or a precision matrix (the inverse of a covariance matrix) in different situations, and the inverse-Wishart the same, but the other way round. It’s already becoming complicated. Hal Stern, coauthor of Bayesian Data Analysis (BDA), helped to clarify many issues for me in an email conversation. In this post I hope to clarify the differences in Wishart parameterizations of BDA, the wikipedia pages, and the WinBUGS and OpenBUGS softwares, and show an example in OpenBUGS where the inverse parameterization has to be specified relative to the distribution’s definition for the correct posterior to result.
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Statistics