Wednesday, August 12th, 2009 exceeded my expectations in so many ways. I was really touched by having so many people in attendance for my dissertation defense. Friends and professors from math & stat, biology, and other departments, collaborators from the medical campus and from consulting outside the university, and my mom and brother. About 25-30 in all.
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Dissertation defense, August 12th
Dissertation defense for Erik Barry Erhardt, PhD candidate in Statistics
Wednesday, August 12th at 10am in Humanities 428
University of New Mexico
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Wishart distribution in WinBUGS, nonstandard parameterization
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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Paper accepted: Prenatal X-ray Exposure and RMS in Children
RA at MIND Institute begins
On Jan 20th, 2009, I joined the Medical Image Analysis Laboratory (MIALab) as a research assistant (RA) at the MIND institute at UNM. This position will transition to a 2-3 year postdoc upon the completion of my PhD this May.
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Paper accepted: Stable Isotope collaboration, Chris Bickford
Christopher P. Bickford, Nate G. Mcdowell, Erik Barry Erhardt, Heath H. Powers, David T. Hanson. (2009)
“High frequency field measurements of diurnal carbon isotope discrimination and internal conductance in a semi-arid species, Juniperus monosperma“.
Plant, Cell & Environment, online
Volume 32, Issue 7, pages 796–810, July 2009.
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Penalized-x, new pool solitaire game
I developed a solitaire game for pool (pocket billiards) that stresses the importance of making every shot count and developing your balls-per-inning potential for those of us who often run between 2 and 10 balls, based on straight pool. I call it “Penalized-x”, where “Penalized-5” would specify 5 penalty balls. The rules:
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The Calamitous Milkcrate Caper, a contra dance
The Calamitous Milkcrate Caper
by Erik B. Erhardt, 2003.05.27
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Original Music from the 1990s
In high school I mostly played guitar, and in college I mostly composed music on the computer. Here’s a selection of that work.
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R> print(“Hello, world”)
[caption id="attachment_34" align="alignright" width="149" caption="C MPI implementation of waves equation on 16 processors, init + 10 time steps."]
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Thanks to Matthew Bohnsack for setting my site up on wordpress. Matt and I worked together on projects in CS 442 Introduction to Parallel Processing in Fall 2006.
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