Posts Tagged ‘ University life ’

What are the distributions on the positive k-dimensional quadrant with parametrizable covariance matrix? (bis)

April 3, 2012
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What are the distributions on the positive k-dimensional quadrant with parametrizable covariance matrix? (bis)

Wondering about the question I posted on Friday (on StackExchange, no satisfactory answer so far!), I looked further at the special case of the gamma distribution I suggested at the end. Starting from the moment conditions, and the solution is (hopefully) given by the system The resolution of this system obviously imposes conditions on those

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simulated annealing for Sudokus [2]

March 16, 2012
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simulated annealing for Sudokus [2]

On Tuesday, Eric Chi and Kenneth Lange arXived a paper on a comparison of numerical techniques for solving sudokus. (The very Kenneth Lange who wrote this fantastic book on numerical analysis.) One of these techniques is the simulated annealing approach I had played with a long while ago.  They seem to use the same penalisation

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IS vs. self-normalised IS

March 11, 2012
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IS vs. self-normalised IS

I was grading my Master projects this morning and came upon this graph: which compares the variability of an importance-sampling estimator versus its self-normalised alternative… This is an interesting case in that self-normalisation does considerably degrade the quality of the approximation in that setting. In other cases, self-normalisation may bring a clear improvement. (This reminded

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di Roma

March 4, 2012
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di Roma

It has been a wonderful week in Roma, a mix of pleasant work and enjoyable free-time! I gave the ABC advanced course for the second time in a month so it did not require much in terms of preparation and there was a good sized audience with attentive (if too silent!) students and friends as

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ABC in Roma [R lab #2]

March 2, 2012
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ABC in Roma [R lab #2]

Here are the R codes of the second R lab organised by Serena Arima in supplement of my lectures (now completed!). This morning I covered ABC model choice and the following example is the benchmark used in the course (and in the paper) about the impact of summary statistics. (Warning! It takes a while to

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ABC in Roma [R lab #1]

February 29, 2012
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ABC in Roma [R lab #1]

Here are the R codes of the R labs organised by Serena Arima in supplement of my lectures. This is quite impressive and helpful to the students, as illustrated by the first example below (using the abc software). I am having a great time teaching this “ABC in Roma” course, in particular because of the

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A Roma

February 25, 2012
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A Roma

Today, I am going to Rome for a week, teaching my PhD course on ABC I first gave in Paris. The course takes place in La Sapienza Università di Roma, from Monday till Thursday. There will be an R lab in addition to the lectures. (I have no further item of information at the moment.)

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Large-scale Inference

February 23, 2012
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Large-scale Inference

Large-scale Inference by Brad Efron is the first IMS Monograph in this new series, coordinated by David Cox and published by Cambridge University Press. Since I read this book immediately after Cox’ and Donnelly’s Principles of Applied Statistics, I was thinking of drawing a parallel between the two books. However, while none of them can

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another X’idated question

February 23, 2012
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another X’idated question

An X’idated reader of Monte Carlo Statistical Methods had trouble with our Example 3.13, the very one our academic book reviewer disliked so much as to “diverse a 2 star”. The issue is with computing the integral when f is the Student’s t(5) distribution density. In our book, we compare a few importance sampling solutions,

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weird [lack of] control…

February 20, 2012
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weird [lack of] control…

When I ran I was expecting the same output as So this means that the dummy index in R “for” loops cannot be tweaked that easily. I seem to remember doing this kind of (dirty) tricks with earlier versions… Now, Alessandra and Robin think this is a good thing that the for loop is robust

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