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USVincent Zoonekynd
 

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  1. USVincent Zoonekynd
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    <p>After studying algebraic geometry, algebraic topology and category theory, after teaching mathematics and computer science in university and high school, after studying bioinformatics and implementing image analysis algorithms in a biotech start-up, I have since been working in finance, in London, Tōkyō and Hong Kong.</p> <p>My preferred programming languages are R and Perl, but I try to use the best language and tools to solve the problem at hand. I also like to learn more marginal languages, such as Haskell or Oz/Mozart. I am interested in human languages, too.</p> <p>Here is a selection of my answers.</p> <ul> <li><p>Computing a probability density function from its <a href="http://stackoverflow.com/questions/10029956/calculating-a-density-from-the-characteristic-function-using-fft-in-r/10038141#10038141">characteristic function</a> or by <a href="http://stats.stackexchange.com/questions/26598/maximum-entropy-sampler/26605#26605">maximizing its entropy</a>;</p></li> <li><p>Quadratic programming <a href="http://stackoverflow.com/questions/9817001/optimization-with-constraints/9817442#9817442">to ensure a sequence is increasing</a> or to <a href="http://stackoverflow.com/questions/9971268/plot-an-item-map-based-on-difficulties/9971741#9971741">position labels on a plot</a></p></li> <li><p>Reparametrizing <a href="http://stackoverflow.com/questions/9666120/constrain-optimisation-problems-in-r/9667097#9667097">optimization problems</a> to make them <a href="http://stackoverflow.com/questions/9592369/in-r-how-do-i-find-the-optimal-variable-to-maximize-or-minimize-correlation-bet/9593809#9593809">unconstrained</a>, for instance <a href="http://stats.stackexchange.com/questions/25007/fitting-the-parameters-of-a-stable-distribution">to fit stable distribution</a>; penalizing them to restrict them to a <a href="http://stackoverflow.com/questions/11110848/how-to-optimize-for-integer-parameters-and-other-discontinuous-parameter-space/11111069#11111069">discrete search space</a></p></li> <li><p>Speeding up computations in R <a href="http://stackoverflow.com/questions/9526691/efficiently-compute-histogram-of-pairwise-differences-in-a-large-vector-in-r/9527046#9527046">using C</a> or by <a href="http://stackoverflow.com/questions/10011425/vectorize-function-to-avoid-loop/10011954#10011954">expanding</a> some of the computations</p></li> <li><p><a href="http://stackoverflow.com/questions/9106401/select-rows-of-a-data-frame-based-on-column-properties/9106581#9106581">Computing the skyline</a></p></li> <li><p><a href="http://stats.stackexchange.com/questions/16631/what-are-essential-rules-for-designing-and-producing-plots/22010#22010">On the use of colour in statistical plots</a></p></li> <li><p><a href="http://stackoverflow.com/questions/9747426/how-can-i-produce-plots-like-this/9748213#9748213">Plotting the result of a time series clustering</a></p></li> <li><p><a href="http://stackoverflow.com/questions/10150161/ordering-117-by-perfect-square-pairs/10150797#10150797">Solving puzzles with graph theory</a></p></li> </ul>
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    1. CODoesn't `as.matrix` suffice?
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      1. POGenerating a simple term.matrix from a dataframe
      1. USVincent Zoonekynd
    2. COThe second step does not look necessary: the `permutations` function has a `v` argument that can directly permute your data, without having to consider the indices: `lapply( 4:6, permutations, n=8, v=LETTERS[1:12] )`.
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      1. POR: Vectorized permutations
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    3. COI think the login name should be "anonymous": what did you use? If you do not specify it, most FTP clients will use your current login name.
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      1. POError when uploading package to CRAN incoming: 550 access denied
      1. USVincent Zoonekynd
 

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