Flowers/Fractals

November 22, 2014
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Flowers/Fractals

Last week, I attended a "Flower Fest" where I had the opportunity to admire several of the most beautiful and awarded flowers, orchids, and decoration plants. Surprisingly, though, I never had thought of flowers like fractals the way I did this time. Fractals attract lots of interest, especially from mathematicians who actually spend some time […]

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Ordinal probit regression: Transforming polr() parameter values to make them more intuitive

November 21, 2014
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Ordinal probit regression: Transforming polr() parameter values to make them more intuitive

In R, the polr function in the MASS package does ordinal probit regression (and ordinal logistic regression, but I focus here on probit). The polr function yields parameter estimates that are difficult to interpret intuitively because they assume a bas...

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“If you’re not using a proper, informative prior, you’re leaving money on the table.”

November 21, 2014
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Well put, Rob Weiss. This is not to say that one must always use an informative prior; oftentimes it can make sense to throw away some information for reasons of convenience. But it’s good to remember that, if you do use a noninformative prior, ...

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Three good charts

November 21, 2014
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Alberto Cairo, Stephen McDaniel and I were asked about our "favorite" data visualization at the Qlik Conference this week. Stephen wrote up our answers here.

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Free Stanford online course on Statistical Learning (with R) starting on 19 Jan 2015

November 21, 2014
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Free Stanford online course on Statistical Learning (with R) starting on 19 Jan 2015

This is an introductory-level course in supervised learning, with a focus on regression and classification methods. The syllabus includes: linear and polynomial regression, logistic regression and linear discriminant analysis; cross-validation and the bootstrap, model selection and regularization methods (ridge and … Continue reading →

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Gelman explains why massive sample sizes to chase after tiny effects is silly

November 21, 2014
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What a lucky day I found time to catch up on some Gelman. He posted about the Facebook research ethics controversy, and I'm glad to see that he and I have pretty much the same attitude (my earlier post is here.). It's a storm in a teacup. Gelman makes two other points about the Facebook study--unrelated to the ethics--which are very important. First, he said: if we happen to see…

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Resampling and permutation tests in SAS

November 21, 2014
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Resampling and permutation tests in SAS

My colleagues at the SAS & R blog recently posted an example of how to program a permutation test in SAS and R. Their SAS implementation used Base SAS and was "relatively cumbersome" (their words) when compared with the R code. In today's post I implement the permutation test in […]

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Visualization of probabilistic forecasts

November 21, 2014
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Visualization of probabilistic forecasts

This week my research group discussed Adrian Raftery’s recent paper on “Use and Communication of Probabilistic Forecasts” which provides a fascinating but brief survey of some of his work on modelling and communicating uncertain futures. Coincidentally, today I was also sent a copy of David Spiegelhalter’s paper on “Visualizing Uncertainty About the Future”. Both are […]

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A short taxonomy of Bayes factors

November 21, 2014
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[Update Oct 2014: Due to some changes to the Bayes factor calculator webpage, and as I understand BFs much better now, this post has been updated …] I started to familiarize myself with Bayesian statistics. In this post I’ll show some insig...

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Erich Lehmann: Statistician and Poet

November 21, 2014
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Erich Lehmann: Statistician and Poet

Memory Lane 1 Year (with update): Today is Erich Lehmann’s birthday. The last time I saw him was at the Second Lehmann conference in 2004, at which I organized a session on philosophical foundations of statistics (including David Freedman and D.R. Cox). I got to know Lehmann, Neyman’s first student, in 1997.  One day, I […]

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Flowers Fractals, or Fractal Flowers

November 21, 2014
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Flowers Fractals, or Fractal Flowers

Last week I attended a “Flower Festival” in Joinville, where I had opportunity to admire several of among the most beautiful and awarded flowers, orchids, and decoration plants. Surprisingly, though, I never had thought on flowers like fractals th...

Read more »

Flowers Fractals, or Fractal Flowers

November 21, 2014
By
Flowers Fractals, or Fractal Flowers

Last week I attended a "Flower Festival" in Joinville, where I had opportunity to admire several of among the most beautiful and awarded flowers, orchids, and decoration plants. Surprisingly, though, I never had thought on flowers like fract...

Read more »

Flowers/Fractals

November 21, 2014
By
Flowers/Fractals

Last week, I attended a “Flower Festival” where I had the opportunity to admire several of the most beautiful and awarded flowers, orchids, and decoration plants. Surprisingly, though, I never had thought of flowers like fractals the way I did this...

Read more »

Flowers/Fractals

November 21, 2014
By
Flowers/Fractals

Last week, I attended a “Flower Festival” where I had the opportunity to admire several of the most beautiful and awarded flowers, orchids, and decoration plants. Surprisingly, though, I never had thought of flowers like fractals the way I did this...

Read more »

Flowers/Fractals

November 21, 2014
By
Flowers/Fractals

Last week, I attended a “Flower Festival” where I had the opportunity to admire several of the most beautiful and awarded flowers, orchids, and decoration plants. Surprisingly, though, I never had thought of flowers like fractals the way I did this...

Read more »

Flowers/Fractals

November 21, 2014
By
Flowers/Fractals

Last week, I attended a “Flower Festival” where I had the opportunity to admire several of the most beautiful and awarded flowers, orchids, and decoration plants. Surprisingly, though, I never had thought of flowers like fractals the way I did this...

Read more »

RNA-seq Data Analysis Course Materials

November 20, 2014
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RNA-seq Data Analysis Course Materials

Last week I ran a one-day workshop on RNA-seq data analysis in the UVA Health Sciences Library. I set up an AWS public EC2 image with all the necessary software installed. Participants logged into AWS, launched the image, and we kicked off the morning ...

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Soil Scientists Seeking Super Model

November 20, 2014
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Soil Scientists Seeking Super Model

I (Bob) spent last weekend at Biosphere 2, collaborating with soil carbon biogeochemists on a “super model.” Model combination and expansion The biogeochemists (three sciences in one!) have developed hundreds of competing models and the goal of the workshop was to kick off some projects on putting some of them together intos wholes that are […] The post Soil Scientists Seeking Super Model appeared first on Statistical Modeling, Causal Inference,…

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Stacking files made easy

November 20, 2014
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Stacking files made easy

Every campaign cycle I usually do similar things, go to a repository, download a bounce of data, merge and store them to an existing RData file for posterior analysis. I've already wrote about this topic some time ago, but this time I think my script became simpler. Set the Directory Let's assume you're not in […]

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Retrospective clinical trials?

November 20, 2014
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Kelvin Leshabari writes: I am a young medical doctor in Africa who wondered if it is possible to have a retrospective designed randomised clinical trial and yet be sound valid in statistical sense. This is because to the best of my knowledge, the assumptions underlying RCT methodology include that data is obtained in a prospective […] The post Retrospective clinical trials? appeared first on Statistical Modeling, Causal Inference, and Social…

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EM algorithm revisited

November 20, 2014
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EM algorithm revisited

On this Tuesday, Professor Xuming He presented their recent work on subgroup analysis, which is very interesting and useful in reality. Think about the following very much practical problem (since the drug is expensive or has certain amount of side effect): If you are given the drug response, some baseline covariates which have nothing to […]

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Christian Robert Shows that the Sample Median Cannot Be a Sufficient Statistic

Christian Robert Shows that the Sample Median Cannot Be a Sufficient Statistic

I am grateful to Christian Robert (Xi’an) for commenting on my recent Mathematical Statistics Lessons of the Day on sufficient statistics and minimally sufficient statistics. In one of my earlier posts, he wisely commented that the sample median cannot be a sufficient statistic.  He has supplemented this by writing on his own blog to show that […]

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The Rise of Bayesian Econometrics

November 19, 2014
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The Rise of Bayesian Econometrics

A recent discussion paper by Basturk et al. (2014) provides us with (at least) two interesting pieces of material. First, they give a very nice overview of the origins of Bayesian inference in econometrics. This is a topic dear to my heart, given that ...

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