Archive for fundamentals

random wake

Posted in Books, Kids, R, Statistics with tags , , , , , , on December 27, 2017 by xi'an

Just too often on X validated, one sees questions displaying a complete ignorance of the basics that makes one purposelessly wonder what is the point of trying to implement advanced methods when missing the necessary background. And just as often, I reacted to the question by wondering out loud about this… In the current case, the question was about debugging an R code for a mixture of two exponential distributions and the random walk Metropolis algorithm that comes with it. Except that the Normal noise was replaced with a Uniform U(0,1) noise, leading to a most obviously transient Markov chain.I eventually corrected the R code, which returned a rather nicely label-switching output. And which did not necessarily help with the comprehension of the fundamentals.

fluctuat nec cogitat

Posted in Kids, pictures with tags on November 21, 2015 by xi'an

stevebellAs was alas predictable, the mass assassinations in Paris last Friday led to senseless gesticulations and warmongering declarations from French political leaders. Hence my title, borrowed from Paris motto: intended to mean “Fluctuating without thinking”, or, as Google translate would inadvertently put it in a strangely appropriate way, to “turn and toss”. Martial emergency order has been declared and is contemplated for months (months!) ahead. After the “Charlie Hebdo” law on intelligence voted a few months ago (which actually goes against everything Charlie stood for!), more attacks on civil liberties are now to come, with a revision of the Constitution with the next days (days!)… Hence this drawing from Steve Bell in The Guardian: While French military forces are engaged in Irak and Syria in a dubious campaign, I completely dispute the notion that France is “at war” and see present declarations and new legislations as catering to the rightmost fringes of the public opinion. With no other clear consequences than to pave the way for the French extreme right to win the coming election(s). Just as withdrawing French citizenship from double nationals who anyway do not consider themselves as French and who are determined to blow themselves on demand is ridiculously inappropriate. The similitude between the reactions of Bush after 09/11/01 and Hollande after 11/13/15 is striking and frightening in the lack of long-term vision and of mere rational thinking… To end up with another translation, “to rock with no purpose”, indeed.