Talk: ACASA Annual meeting 2011

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. A Bayesian Framework for Stable Isotope Mixing Models Erik B. Erhardt, The Mind Research Network; Edward J. Bedrick, Division of Epidemiology and Biostatistics, University of New Mexico Health Sciences Center Stable isotope sourcing is used to estimate proportional contributions of sources to a mixture, such as in the analysis of animal diets and plant nutrient use. Statistical methods for inference on the diet proportions using stable isotopes have focused on the linear mixing model. Existing frequentist methods provide inferences when the diet proportion vector can be uniquely solved for in terms of the isotope ratios. Bayesian methods apply for arbitrary numbers of isotopes and diet sources but existing models are somewhat limited as they assume that trophic fractionation or discrimination are estimated without error or that isotope ratios are uncorrelated. We present a Bayesian model for the estimation of mean diet that accounts for uncertainty in source means and discrimination and allows correlated isotope ratios. This model is easily extended to allow the diet proportion vector to depend on covariates, such as time. Two examples are used to illustrate the methodology.
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Youth dancing, spring 2011

I’m happy to write about two touching events consistent with my vision that I helped organize the last few months: teaching middle schoolers folk dance, and organizing a youth-led contra in Santa Fe. Rob Campbell invited me into his 4th-5th-6th grade class at the Montessori of the Rio Grande Charter School to teach folk dance.  As a dance leader, I’m still pretty green, but I have a real passion for bringing dance to the next generation.  So without any preparation, other than thinking about how to help kids dance together, I went in with my headset mic, my battery-powered amplifier, a few index cards, and my enthusiasm and positive attitude.  Rob had already done some great preparation with the kids, letting them know about calls that are in 8 beats and so on.  He’s a long-time dancer and does the sound at many of the Albuquerque dances.  His wife, Deb, has been a pivotal figure, too, organizing “Boo camp” and many other things in our community.  When I arrived, the kids were ready to dance.  I talked a bit about music and the structure of a dance, but got them moving pretty quickly.  I wasn’t expecting some of the challenges, such as reluctance to hold hands between selected people and social structure (friends, not friends, etc.) that would be a powerful force for who was willing to dance with whom.  However, calling dances where the kids kept their partners (reels, circle mixers without the “mix”) usually worked just fine, and having the partner anchor I think was helpful for beginners.  Oh, and the word “partner” — I quickly starting saying “pair” because they didn’t want it to sound like they were dating or anything.  Rob reported back, “The children loved it, and I even got some feedback from parents because their children are talking about how fun it was at home.  A few children were even practicing some of the moves yesterday at school!” We had several weeks together in school, but we both wanted the kids to dance to live music out in the world.  On March 5th we had a 6-7pm pre-contra dance in Albuquerque with his class, and some of the parents danced, too.  The McPapenhagen’s played for us (Gary Papenhagen, Scott Mathis, and Linda Mathis).  The kids loved, loved, loved the live music!  We danced several dances, concluding with a donut dance one of the kids wrote!

Donut formation dance Anastasia and Erik Erhardt Type: Reel Formation: Donut (longways set, bent into a circle) Level: Beginner

A1 ———– (8) Partner allemande Right 1X (8) Partner allemande Left 1X A2 ———– (8) Right-diagonal Do-si-do (8) Left-diagonal Do-si-do B1 ———– (8) Partner two-hand turn 1X or 2X (8) Right-diagonal right-elbow turn 1X B2 ———– (8) Left-diagonal right-elbow turn 1X (8) Partner Do-si-do C ———– (32) Sashay the donut

Notes: C: Sashay the donut – choose a couple, they sashay between the lines, each subsequent couple following them, backing out when they return home.  It effectively turns the donut inside out.
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Richard Wilson: All join hands, thirty years of community dance

“All join hands” by Richard Wilson

with Erik Erhardt and Lauren Lamont

This book tells the story of Richard Wilson’s start and many contributions as a dance leader in the country dance community. Included are dances, stories, pictures, and poems, all bringing to life the many ways Richard has touched our lives. If you would like to make a contribution to the book, there are three ways.  (1) Tell us a specific way Richard has enriched the community, and enriched your life and made it more wonderful.  Stories may be written (1-4 pages) or be a short audio recording (4-10 minutes) which we will transcribe and give to you to edit.  (2) Do you have good pictures you’d be willing to share?  We can take physical pictures to scan. With each photo please provide photo credits, location, date, event, and an anecdote for the photo caption.  (3) Who else should I contact who might like to contribute a story? Contact Lauren Lamont for more information, or to provide a contribution. March: There is still time to contribute… Richard Wilson demonstrates an example of his drumming/dancing healing rhythms. Jim Boros has these videos of Richard:
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Contra dance: Left-hand Gypsy

Left-hand Gypsy Erik Erhardt Type: Contra Formation: Duple-Indecent Level: Easy-Int A1 ———– (4) Partner Swat the Flea, (left-hand box-the-gnat) (4) Partner Swat the Flea back (8) Star Left 3/4 with same neighbors (partners on lady’s home side) A2 ———– (8) Partner left-hand gypsy (8) Partner right-shoulder swing B1 ———– (4) Gents forward (4) Gents balance a long wavy line of gents, stay in wavy line (4) Ladies cast over their right shoulder, then forward (to the left of their partner) (4) Ladies balance a long wavy lines of ladies B2 ———– (8) New neighbors, Gypsy star 3/4, Gents drop right back up, Ladies drop left walk forward (8) Neighbor swing (on everyone’s home side) Notes: A2 – Left-hand gypsy (like a right-hand gypsy) has left hand at your waist, palm facing your own hip, and linked with your partner as you gypsy.  Turn this into a swing by pulling the joined left hand into an allemande position, put right hand on partner’s right shoulder, and reverse body momentum to swing in usual direction. Other Notes: The handed-gypsy comes from Richard Wilson’s “Right hand Gypsy”, the sexiest move in contra.  Written for Katherine Sanden.
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Contra dance: Sashay, Sassy Kat

Written for Katherine Sanden, who wrote me a song.  She likes the traditional “reel” dances that have a couple down the center with all the attention.  I ruin that by having the other folks swing during the sashay down, but redeem myself with the leapfrog move (that Heather Carmichael came up with).  And if you like a hay, there’s two of them! Sashay, Sassy Kat Erik Erhardt Type: Contra Formation: Four Facing Four Level: Int A1 ———– (16) Partner balance and swing, end facing original direction A2 ———– Outsides (16) Corner balance and swing WHILE Insides (4) Corner balance (4) Sashay down 4 slides (4) Leapfrog (tops arch, bottoms dive up through) (4) Sashay up 4 slides to progressed place B1 ———– (8) 1/2 Hey ACROSS the set with 4-some, centers passing right shoulders (8) In groups of 4, circle RIGHT 1X B2 ———– (16) Full Hay UP AND DOWN set with neighbors, Ladies passing left shoulder Notes: A1 – start and end in same place A2 – facing lines of four end progressed up and down set B1 – each line of four has reversed their order across the hall B2 – start and end in same place
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Contra dance: Voyager

Voyager Erik Erhardt Type: Contra Formation: 4-facing-4 Becket-CW Level: Int A1 ———– (8) Right hands-across star (8) Gents drop out, ladies turn 1/2 to chain to partner A2 ———– (16) Grand Hay, ladies start by right shoulders and continue across to neighboring set. B1 ———– (4) Balance the ring (4) Pass through across the set (8) Partner swing (couples are at “home” position in other set) B2 ———– (8) Long lines, forward and back (8) Right hands-across star, gents lead partner up/down set to progress into new star Notes: Start as a 4-facing-4 dance, then in small circles of 4, turn a quarter to left to be in Becket formation.  Your couple and your “same 4-some” couple are in neighboring sets facing in the same direction across the set. A2 – maybe teach grand hay with hands to help clarify where everyone is going. A2 – Couples are in original positions facing in to their own sets.  If you are an “outside” couple, you will end as an outside couple in the neighboring set, same for an “inside” couple.  The hey starts like a normal hay, but instead of turning around on the “inside” side, you keep going weaving all the way over to the other set. Other Notes: Adapted from “Star Trek” by Mike Richardson.
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Paper published: A baseline for the multivariate comparison of resting state networks

In this paper we’ve put together a cohort of so-called “healthy normal controls” in the largest single group independent component analysis (ICA) forward model. Included in our analysis approach is a statistical methodology for performing mancova when the number of fMRI brain voxels (roughly V=60K) to test for activation differences over demographic variables is much larger than the number of subjects (N=603).  This massive project involved researchers nearly spanning our Medical Image Analysis Laboratory (MIALab), but many other investigators at the Mind Research Network (MRN).  It is a great example of what makes collaboration fun, challenging, and productive (thank you Elena, Eswar, Bill, Judith, Martin, and Srinivas). A baseline for the multivariate comparison of resting state networks Citation:Allen EA, Erhardt EB, Damaraju E, Gruner W, Segall JM, Silva RF, Havlicek M, Rachakonda S, Fries J, Kalyanam R, Michael AM, Caprihan A, Turner JA, Eichele T, Adelsheim S, Bryan AD, Bustillo J, Clark VP, Feldstein Ewing SW, Filbey F, Ford CC, Hutchison K, Jung RE, Kiehl KA, Kodituwakku P, Komesu YM, Mayer AR, Pearlson GD, Phillips JP, Sadek JR, Stevens M, Teuscher U, Thoma RJ and Calhoun VD (2011). A baseline for the multivariate comparison of resting state networks. Front. Syst. Neurosci. 5:2. doi: 10.3389/fnsys.2011.00002 Received: 16 Jun 2010; Accepted: 03 Jan 2011; Published online: 04 Feb 2011. Abstract As the size of functional and structural MRI datasets expands, it becomes increasingly important to establish a baseline from which diagnostic relevance may be determined, a processing strategy that efficiently prepares data for analysis, and a statistical approach that identifies important effects in a manner that is both robust and reproducible. In this paper, we introduce a multivariate analytic approach that optimizes sensitivity and reduces unnecessary testing. We demonstrate the utility of this mega-analytic approach by identifying the effects of age and gender on the resting state networks of 603 healthy adolescents and adults (mean age: 23.4 years, range: 12 to 71 years). Data were collected on the same scanner, preprocessed using an automated analysis pipeline based in SPM, and studied using group independent component analysis. Resting state networks were identified and evaluated in terms of three primary outcome measures: time course spectral power, spatial map intensity, and functional network connectivity. Results revealed robust effects of age on all three outcome measures, largely indicating decreases in network coherence and connectivity with increasing age. Gender effects were of smaller magnitude but suggested stronger intra-network connectivity in females and more inter-network connectivity in males, particularly with regard to sensorimotor networks. These findings, along with the analysis approach and statistical framework described here, provide a useful baseline for future investigations of brain networks in health and disease.
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Erik and Karina teaching couples dance in CA in July

Last year (2010) a group of us younger folks (me, Karina and Laurel Wilson, Lauren Lamont, Mia Bertelli, and Zoe Kelly Linkletter) were invited out to a wonderful camp in California.  We had an amazing time and this year Karina and I are on staff teaching couples dance! BACDS American Dance and Music Week, Sunday-Friday, July 3–8, 2011 Waltz and Scandinavian couples dancing workshop These series of workshops led by Karina Wilson and Erik Erhardt on couples dances that often accompany an evening of contra dance, such as waltz, Scandinavian, polka, and others, will emphasize connecting with your partner and the music, becoming strong on the basic form of each dance, and developing a vocabulary of moves for variety and play. In the waltz series we will work on form and flow, clear (body) communication with a partner, getting in and out of positions, and stringing moves together into vignettes that delight.  In the Scandinavian series we will learn dances to accompany music in quadruple and duple meter (4/4 and 2/2) such as schottische, snoa, and polka, and triple meter (3/4 and 6/8) such as hambo, polska, and mazurka.  Each workshop will focus one or two dances.  For all dances, those who wish to become more “bidancual” (able to dance both gender roles) are very much encouraged to dance the less familiar role when they wish. Erik Erhardt instructs couples dancing in New Mexico before weekly contra dances and at dance camps.  His years of teaching experience, attention to detail, and ability to provide multiple explanations help the learning dancer understand, connect with the dance, and ultimately dance the dance.  Erik also calls contra, English, and squares, and helps create opportunities for youth leadership in the folk dance and music community, and is generally a positive leader on and off the floor. Growing up the daughter of a caller in the Contra and English Country dance community in the heart of New Mexico, Karina Wilson is not lacking in folk dance and couples dance exposure or knowledge. Formally trained in Haitian, West African, Zimbabwean, and Gumboot, she has tried her hand Latin couples dances, Swing, lindy, blues, Flaminco, afro-brazillian, stilt dance, modern, Balinese, Capoera, and samba. She is the co-choreographer for the Santa fe youth based All species day stilt troupe, and for Santa Fe DjunDjun dance. She has taught with the Santa Fe late nighters, a Salsa and swing group, and co teaches a waltz workshop with Erik Erhardt on a weekly basis. She currently dances with Moria Guinean dance troupe. With over 20 years of Classical violin experience and 15 years of playing for Contra and English country dances, she teaches Violin for the Santa Fe youth symphony and the Santa Fe concert association, and plays for English and Contra in her local and neighboring communities.
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Everyone’s written a poem or two.  In my early 20s, I wrote a lot.  Yeah, I was the guy who toted around a copy of the concise OED and set it next to my clipboard with stacked empty pages, filling them slowly, turning them over, and refreshing my English breakfast tea every couple hours.  Like many, writing helped shape my thoughts about myself and the world around me — my living, vital, dynamic quality.  I don’t claim any of it is any good; actually, most of it is in the range of bad to so-so.  If you’re just going to peek, I recommend diving into the 1998-2001 range:  ErikBarryErhardt_poetry_selected.pdf.
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Acumen in Statistics