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Posts

April 21, 2014

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7:30 AM | What Nate Silver's critics are actually saying
Regarding the ongoing 538 discussion, it appears that we may be talking across each other in this case (from a previously mentioned comment by Kaiser Fung):"The level of rigor that Krugman and others demand requires years, perhaps decades, of research to write one piece; meanwhile, the other critique is the content is not timely. Think about the full-time journalists he has hired - there isn't a way to pay them enough to do the kind of pieces that are being imagined. As we all know, data […]
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6:00 AM | Quick & Dirty – Cerchi nei quadrati, sfere nei cubi and so on…
Qui non è la prima risposta che è sbagliata: è la risposta giusta, che è sbagliata… Cominciamo con N=2. Prendete un quadrato, dividetelo in quadranti. Tracciate i quattro cerchi inscritti in ognuno dei quadranti. Al centro del quadrato originale, tracciate il cerchio tangente ai quattro cerchi inscritti. Non dovreste avere problemi a calcolare il raggio di [...]
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6:00 AM | 5769
5769 = 3 x 3 x 641.5769 is the number of permutations of nine elements that have a third power equal to the identity permutation (A001470).5769 is the number of binary strings of length 14 with no substrings equal to 0001 or 1000 (A164398).5769 has a representation as a sum of two squares: 5679 = 122 + 752.5769 divides 10016 - 1.5769 is the number of (unordered) ways of making change for n cents using coins of 1/2, 1, 2, 3, 5, 10, 20, 25, 50, and 100 cents (all historical U.S. coinage […]
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5:00 AM | Dans Hamlet...
Shakespeare a 450 ans. Peu de mathématiques dans Hamlet... mais une histoire de pari à éclaircir. - Mathématiques ailleurs / Piste verte, featured, Mathématiques et littérature
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5:00 AM | Random forests with random projections of the output space for high dimensional multi-label classification
It started in 2009 when John Langford and colleagues noted that label vectors were sparse and that using techniques of compressive sensing one could reduce learning in large dimensional space. Here is a new entrant in this area:Random forests with random projections of the output space for high dimensional multi-label classification by Arnaud Joly, Pierre Geurts, Louis WehenkelWe adapt the idea of random projections applied to the output space, so as to enhance tree-based […]
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4:39 AM | A Preview of Barbados/Bellairs
This post is probably not so interesting unless you plan to travel to the Caribbean in a few weeks. The website for the conference is offline, so I thought I might update attendees on what might be happening, at least … Continue reading →
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4:24 AM | Bellman Confirms A Suspicion
As is by now well-known, I regard the supposed opposition between static and dynamic languages as a fallacy: the latter, being a special case of the former, can scarcely be an alternative to it.  I cannot tell you how many times I’ve been handed arguments along the lines of “oh, static languages are just fine, but I want […]
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3:45 AM | Cross-validation in finance, psychology, and political science
A large chunk of machine learning (although not all of it) is concerned with predictive modeling, usually in the form of designing an algorithm that takes in some data set and returns an algorithm (or sometimes, a description of an algorithm) for making predictions based on future data. In terminology more friendly to the philosophy […]

Bailey, D., Borwein, J., de Prado, M.L. & Zhu, Q. (2014). Pseudo-Mathematics and Financial Charlatanism: The Effects of Backtest Overfitting on Out-of-Sample Performance, Notices of the American Mathematical Society, 61 (5) 458. DOI:

Citation
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3:16 AM | perspective
Sometimes it’s nearly 10 pm on a Sunday night and I’m doing things like reading “Seven Ways to Re-ignite the Spark in Your Relationship!” and mentally search-and-replacing all the parts about a significant other with teaching math. I do think it would be worthwhile, at some point, to do something like catalogue all of the coping mechanisms […]
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3:05 AM | On This Day in Math - April 21
A drunk man will find his way home, but a drunk bird may get lost forever.From Colloquial catchy statements encoding serious mathematics at Math Overflow.[ The serious math...A 2-dimensional random walk is recurrent (appropriately defined for either the discrete or continuous case) whereas in higher dimensions random walks are not. More details can be found for instance in this enjoyable blog post by Michael Lugo.  "This particular saying, by the way, is usually attributed to […]
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3:00 AM | Monday Puzzle: How many odd-even sequences are there?
From the numbers 1, 2, … n, start by writing an odd number, and keep writing larger numbers–alternating between even and odd–until you stop at n. Call this an odd-even sequence of n. For example, if n = 3, then the only odd-even sequences are 123 and 3. If n = 8, then the sequences […]
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2:58 AM | ICM Survey: Sum-of-squares proofs and the quest toward optimal algorithms
I have just posted online a new survey “Sum-of-Squares proofs and the quest toward optimal algorithms” co-authored with David Steurer . The survey discusses two topics I have blogged about before – Khot’s Unique Games Conjecture (UGC) and the Sum-of-Squares (SOS) method – and the connections between them. Both are related to the notion of meta algorithms. […]
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2:57 AM | How do they make a bug like this?
For a small project I needed to solve a very small QP model. As the input and output were in Excel, it made some sense to try Excel’s Solver. One of the constraints is: The way to do this is to create a cell with the sum and then use Solver.SolverAdd to add a constraint. The complete call can look like:Call Solver.SolverAdd(CellRef:=sumcell, Relation:=2, FormulaText:=1)See http://msdn.microsoft.com/en-us/library/office/ff838657(v=office.14).aspxUnfortunately (for me) this did not work and I […]
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1:37 AM | #2minPD Project: Using ThingLink for Pre-Teaching
Thanks to a connection fostered by my pal Guido over at Nearpod, I found out about a unique opportunity to do global professional development in 2 minutes flat.  The #2minPD project is the brain-child of Stanford fellow Melissa Pelochino, whose goal … Continue reading →
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1:09 AM | FINALLY!!!  I got 2048!!!  YES!!!  FUCK YEAH!!!  Hey, where did...
FINALLY!!!  I got 2048!!!  YES!!!  FUCK YEAH!!!  Hey, where did my family go…
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1:08 AM | The best book written on education in the late 20th century
is The Phantom Tollbooth, by Norton Juster. It describes deep issues that thoughtful educators wrestle with daily: wisdom, friendship, trust, relationships between children and adults, and most importantly, knowledge.I remember it as one of my favorite books growing up, but I hadn't reread it in years. Lately, I've taken to reading to my daughter again before her bedtime, and I decided that I would read her books I thought she should know about but might not pick up on her own. I started with […]
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12:30 AM | I’m Going To TeachFest!
An email I’d been anxiously hoping for arrived in my inbox on Friday night. Dear Kyle,Congratulations! We are delighted to inform you that you have been selected to join LearnZillion’s 2014 Dream Team! It was longer than that, of course, but all I really needed to read was the first line.  I’m one of 200 teachers […]

April 20, 2014

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11:41 PM | Brutal honesty: Author takes to PubPeer to announce retraction — and tells us she’ll lose PhD, professorship
Over the past week, there have been a number of comments on PubPeer — a site of which we’re big fans — about a 2007 paper in Oncogene. The comments suggested that the figures in the paper had problems. Some bands seemed to be duplicated, and one of the images looked very much like that […]
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11:40 PM | Removing ‘Barriers’ to Education through Free College Textbooks
Removing ‘barriers’ to education through free college textbooks By Emanuella Grinberg, CNN April 18, 2014 Link to article
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11:16 PM | OKCathy
This week’s Aunt Pythia column features Cathy O’Neil’s take on what questions online daters ought to have to answer in their profiles: How sexual are you? (super important question) How much fun are you? (people are surprisingly honest when asked this) How awesome do you smell? (might need to invent technology for this one) What bothers […]
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11:00 PM | Notes on evaluating predictions, or Background to my airfare predictor article
My article on whether we can trust airfare prediction models is published today at FiveThirtyEight, the new data journalism venture launched by Nate Silver after he moved to ESPN. This topic was originally conceived as a chapter of Numbersense (link) but I dropped it. As I have noted in my review of Nate Silver's book, he has a keen interest in evaluating predictions, and not surprisingly, he encouraged me to get this piece done. Putting Big Data to the Test Just like Google Flu Trends (link), […]
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10:58 PM | Linkfest for Sunday, April 20 (a small one)
Nat Banting on making practice more conceptual - ask students to do the last step in posing the problem. Nice!Andrew Knauft descrbies why he thinks Geogebra > Desmos. A site for finding, building, and storing formulas online, Formula Sheet. (hat tip to Glenn Waddell, whose diigo account may have inspired me to get one - which I don't use. Maybe I should ask him to teach me how to make it useful. I love his real posts, but his Diigo Links (Weekly) are often full of useful ideas too.)Malke […]
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10:43 PM | Remembering Nina Cassian
Exiled Romanian poet Nina Cassian (1924-2014) died last week in Manhattan.  Cassian was an outspoken poet whom I admired for her political views; she also was connected to mathematics -- in her subject matter and her friends.  (See, for example, this posting from January 31, 2011.)       Equality     by Nina Cassian       If I dress up like a peacock,       you dress like a […]
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10:14 PM | a day for comments
As I was flying over Skye (with [maybe] a first if hazy perspective on the Cuillin ridge!) to Iceland, three long sets of replies to some of my posts appeared on the ‘Og: Dan Simpson replied to my comments of last Tuesday about his PC  construction; Arnaud Doucet precised some issues about his adaptive subsampling […]
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9:36 PM | Some Cute Integrals — U-Substitutions
Students of an introductory college-level Calculus sequence may eventually take a “Calculus II” course. This course is a main stay in the Engineering disciplines as well as a major in Mathematics. One of the main topics covered in this course is techniques of integration — u-substitution, integration by parts, trigonometric substitutions and trigonometric integrals, integration […]
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8:53 PM | Photo
No summary available for this post.
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8:44 PM | Sistemi di disequazioni (anche di 2 grado) | Chi ha paura della matematica
Esercizi da svolgere sui sistemi di  disequazioni leggi articolo completo
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8:39 PM | Esercizi sulle disequazioni fratte | Chi ha paura della matematica
Esercizi da svolgere sulle disequazioni fratte di secondo grado. leggi articolo completo
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8:19 PM | Cost of light bulbs – New and improved
There’s a lot of misinformation out there about the cost to consumers of CFL and LED bulbs and the savings in energy and money that could be realized. Let your students “do the math” and realize some of the profit…Read more →
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8:04 PM | Teach Yourself Logic, new layout
The Teach Yourself Logic Guide has a new look. Now, instead of being a standard A4 PDF, it should be an ideal size for reading on screen. Read it either (i) on an iPad (download in Safari, open e.g. in … Continue reading →
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