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# Posts

### October 23, 2014

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One of my favorite old movies is the “The African Queen” with Humphrey Bogart (he played Charlie) and Katherine Hepburn (she played Rose). In that movie, Rose asks Charlie “Could you make a torpedo?” and Charlie responds: “A torpedo?…You don’t … Continue reading →
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Daniel Taylor-Rodriguez is a new postdoctoral fellow at SAMSI and is participating in the Ecology program this year. He came from the University of Florida. His wife, Natalia, is still in Gainesville currently working on her Ph.D. in animal science. … Continue reading →
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John Conway likes playing with the Fibonacci sequence. He invented many new sequences using the following trick. The next number in the sequence is the sum of the two previous number adjusted in some way. Free Fibonacci sequences were invented this way. Here is the recurrence for an n-free Fibonacci sequence: the next number in […]
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In the in-class applied statistics qualifying exam, students had 4 hours to do 6 problems. Here were the 3 problems I submitted: In the helicopter activity, pairs of students design paper ”helicopters” and compete to create the copter that takes longest to reach the ground when dropped from a fixed height. The two parameters of the […] The post Some questions from our Ph.D. statistics qualifying exam appeared first on Statistical Modeling, Causal Inference, and Social Science.
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[picking up where we left off here]David Brooks has one of the most desirable jobs in journalism; it is also one of the most difficult. He has to present a mainstream conservative perspective in a way that appeals to his center-left target audience (which includes but is somewhat larger than the target audience of the New York Times). His job is greatly complicated by shifts in the Republican Party and the conservative movement. On a growing number of issues there is less and less common ground […]
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Rui just sent me the following:  Hi Igor, Not sure if this is the appropriate way to do it, but I wanted to (shamelessly) point you (and the readers of nuit blanche) to our recent work on adaptive compressive sensing for structured sparsity: http://arxiv.org/abs/1410.4593 In this work we investigate the problem of estimating the support of structured signals via adaptive compressive sensing. We examine several classes of structured support sets, and characterize the signal strength […]
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I’ve been heads down writing this week but I wanted to share a bunch of great stuff coming out. Here’s a great interview with machine learning expert Michael Jordan on various things including the big data bubble (hat tip Alan Fekete). I had a similar opinion over a year ago on that topic. Have you […]
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As we've written about before, mitochondria generate the energy required by our cells through respiration that involves using an "electrochemical gradient" as an energy store (a bit like pumping water up into a reservoir for energy storage to then harness it flowing down the gradient of a hill to turn a turbine), and produces free oxygen radicals as by-products (a bit like sparks when the engine is running hot). The fundamental importance of this machinery which not only delivers energy, but is […]

### October 22, 2014

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As usual, you can find everything on the Stan Home Page. Drop us a line on the stan-users group if you have problems with installs or questions about Stan or coding particular models. New Interfaces We’d like to welcome two new interfaces: MatlabStan by Brian Lau, and  Stan.jl (for Julia) by Rob Goedman. The new […] The post Stan 2.5, now with MATLAB, Julia, and ODEs appeared first on Statistical Modeling, Causal Inference, and Social Science.
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My weight loss progress is progress no more. I am stuck at 225. I have my morning routine. I wake up and jog to the facilities; then I weigh myself. Why do I do this in this order? Because I do not use an alarm-clock. I depend on my own hydro-alarm that wakes me up […]
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Let $p \in \mathbb {Z}[X]$ and of fifth degree with only the terms for $x^5$, $x^4$ and $x^3$ known, the terms for $x^2$, $x$ and $1$ are not known. $$p=x^5 - 5x^4 - 35x^3 + \cdots$$ The ( five ) roots of $p$ form an arithmetic sequence. Find the roots of $p$.
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Recently I had a disagreement with Larry Bartels which I think is worth sharing with you. Larry and I took opposite positions on the hot topic of science criticism. To put things in a positive way, Larry was writing about some interesting recent research which I then constructively criticized. To be more negative, Larry was […] The post Sailing between the Scylla of hyping of sexy research and the Charybdis of reflexive skepticism appeared first on Statistical Modeling, Causal Inference, […]
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Many engineering textbooks such as Ogata’s Modern Control Engineering include small code examples written in languages such as MATLAB. If you don’t have access to MATLAB and if the examples don’t run in GNU Octave for some reason, the value of these textbooks is reduced. Professor Kannan M. Moudgalya et al of the Indian Institute of [...]
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I'm just a good ol' Arkansas boy (and a lapsed Presbyterian to boot) so I don't know from Yiddish, but for anyone discussing education reform, this one is indispensable.From the inexplicably good Cracked.com:#8. "Farpotshket" (Yiddish) What It Means: Something that was a little bit broken ... until you tried to fix it. Now it's totally screwed.To demonstrate the usefulness of "farpotshket," look no further than that nightstand you picked up at your friendly neighborhood IKEA. You […]
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Marc Andreessen has a new interview up and it is characteristically packed with silliness. If things had gone better for ViolaWWW, do you think Pei-Yuan Wei would have gotten this annoying?What did you do?I just went to college. I did my thing. I came out here in ’94, and Silicon Valley was in hibernation. In high school, I actually thought I was going to have to learn Japanese to work in technology. My big feeling was I just missed it, I missed the whole thing. It had happened in […]
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Kiran Varanasi mentioned it on the Google+ Community. He also said: Compressed manifold modes are compressed eigenfunctions of the Laplace-Beltrami operator on 3D manifold surfaces. They constitute a novel functional basis, called the compressed manifold basis, where each function has local support. We derive a method, based on ADMM, for computing compressed manifold modes (CMMs) for discrete polyhedral 3D meshes. We show that CMMs identify key shape features, yielding an intuitive […]
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Here’s a clever example from Paul Nahin’s new book Inside Interesting Integrals. Suppose you want to evaluate Since the range of integration is symmetric around zero, you might think to see whether the integrand is an odd function, in which case the integral would be zero. (More on such symmetry tricks here.) Unfortunately, the integrand […]
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I love having young engineers on my team. I also love cookies and we occasionally have cookies at some of our meetings – people might not attend otherwise, including me. However, our cookie selection is generally not particularly inspired. One … Continue reading →

### October 21, 2014

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Luckily I keep good backups. But recently I started Firefox and it said something like "you haven't used firefox in a while, would you like to start over with a new profile to take advantage of our new features?" So since I mostly use Chromium, I said, "yes". Days later I tried to start Zotero […]
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Reference: Moore, Thomas A., A General Relativity Workbook, University Science Books (2013) – Chapter 21, Problem 21.7. According to the Einstein equation, the Riemann tensor in 2D must be zero in empty space, implying that gravitational fields cannot exist in 2D. Another consequence of the Einstein equation is that the stress-energy must be zero on […]
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Over in Canada, Frances Woolley takes on the question of should the elimination of the deficit lead to immediate tax cuts.  Seriously.  Read and marvel at these quick facts:From 2008–09 through 2013–14, the Government has delivered tax reductions totalling more than \$60 billion to job-creating businesses. According to KPMG, total business tax costs in Canada are now the lowest in the Group of Seven (G-7) and 46% lower than those in the United States. Personal income taxes are now […]
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This time we use the principle of minimum power to determine what a circuit made of resistors actually does. Its ‘behavior’ is described by a functor sending circuits to linear relations between the potentials and currents at the input and output terminals. We call this the ‘black box’ functor, since it takes a circuit: […]
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Today I am introducing Badger Bracketology: http://bracketology.engr.wisc.edu/ I have long been interested in football analytics, and I enjoy crunching numbers while watching the games. This year is the first season for the NCAA football playoff, where four teams will play to determine the National Champion. It’s a small bracket, but it’s a start in the right direction. […]
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Joe Simmons writes: I asked MTurk NFL fans to consider an NFL game in which the favorite was expected to beat the underdog by 7 points in a full-length game. I elicited their beliefs about sample size in a few different ways (materials .pdf; data .xls). Some were asked to give the probability that the better […] The post Try a spaghetti plot appeared first on Statistical Modeling, Causal Inference, and Social Science.
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On a recent visit to California Polytechnic State University, I met a lot of great folks and was asked several good questions about teaching and learning. Here are some of my answers.
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[Originally posted at You Do the Math]A few years ago I taught at a small rural school in the Mississippi Delta. The old timers would talk at great length about how much better the school had been before I got there. They attributed the decline to the closing of the alternative school. In the "good old days," any student who caused trouble would be pulled out of class and sent to a special, highly structured school -- basically a glorified study hall -- run by an honest-to-God former Marine […]
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Reference: Moore, Thomas A., A General Relativity Workbook, University Science Books (2013) – Chapter 19; Box 19.6. As an example of calculating the Ricci tensor and curvature scalar we’ll find them for the 2-d surface of a sphere. The Ricci tensor is calculated from the Riemann tensor, and that in turn depends on the Christoffel […]
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We have all heard stories of the  fire hazards that lithium-ion batteries present – just to remind you, here is a partial list: Boeing Dreamliner Electric Cars Samsung Phones There have been many other documented “thermal events”. I personally have … Continue reading →
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I guess my first posted rant was the call for papers thing.  Here's a second.Countless times, from me to Chair/Dean xxx at Some Other University: I am happy to help with your evaluation of Professor zzz. This email will serve as my letter. [email here]...Countless times, from Chair/Dean xxx to me: Thanks very much for your thoughtful evaluation. Can you please put it on your university letterhead and re-send?Fantasy response from me to Chair/Dean xxx:Sure, no […]
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This is a guest post by Luis Daniel, a research fellow at The GovLab at NYU where he works on issues dealing with tech and policy. He tweets @luisdaniel12. Crossposted at the GovLab. What is Evidence-based Sentencing? For several decades, parole and probation departments have been using research-backed assessments to determine the best supervision and treatment […]