Archive for Le Monde

the other end of statistics

Posted in Books, pictures, Statistics with tags , , , , , , on February 8, 2017 by xi'an

A coincidence [or not] saw very similar papers appear in Le Monde and The Guardian within days. I already reported on the Doomsday tone of The Guardian tribune. The point of the other paper is essentially the same, namely that the public has lost trust in quantitative arguments, from the explosion of statistical entries in political debates, to the general defiance against experts, media, government, and parties, including the Institute of Official Statistics (INSEE), to a feeling of disconnection between statistical entities and the daily problems of the average citizen, to the lack of guidance and warnings in the publication of such statistics, to the rejection of anything technocratic… With the missing addendum that politicians and governments too readily correlate good figures with their policies and poor ones with their opponents’. (Just no blame for big data analytics in this case.)

career advices by Cédric Villani

Posted in Kids, pictures, Travel, University life with tags , , , , , , on January 26, 2017 by xi'an

athens1
Le Monde has launched a series of tribunes proposing career advices from 35 personalities, among whom this week (Jan. 4, 2017) Cédric Villani. His suggestion for younger generations is to invest in artificial intelligence and machine learning. While acknowledging this still is a research  topic, then switching to robotics [although this is mostly a separate. The most powerful advice in this interview is to start with a specialisation when aiming at a large spectrum of professional opportunities, gaining the opening from exchanges with people and places. And cultures. Concluding with a federalist statement I fully share.

a perfect fit

Posted in Books, Statistics with tags , , , , on January 25, 2017 by xi'an

perfitHere is the table that kept most French commentators on the primaries busy on Monday, since the fit of the results at 10am to the results at the previous midnight is perfect, indicating the 10am results are not results… There was even a line in Le Monde about achieving this perfect fit being of order 10⁻³, “un miracle statistique de l’ordre d’une chance sur mille”, although no details of this arcane calculation are provided! I wonder why a journalist writing about nonsensical data feels obliged to add more nonsensical data to “support” one’s argument. [Thanks to Arthur Charpentier for sending me the data.]

Le Monde puzzle [#990]

Posted in Books, Kids, pictures, Statistics, Travel, University life with tags , , , , on January 12, 2017 by xi'an

To celebrate the new year (assuming it is worth celebrating!), Le Monde mathematical puzzle came up with the following:

Two sequences (x¹,x²,…) and (y¹,y²,…) are defined as follows: the current value of x is either the previous value or twice the previous value, while the current value of y is the sum of the values of x up to now. What is the minimum number of steps to reach 2016 or 2017?

By considering that all consecutive powers of 2 must appear at least one, the puzzles boils down to finding the minimal number of replications in the remainder of the year minus the sum of all powers of 2. Which itself boils down to deriving the binary decomposition of that remainder. Hence the basic R code (using intToBits):

deco=function(k=2016){
 m=trunc(log2(k))
 while (sum(2^(0:m))>k) m=m-1
 if (sum(2^(0:m))==k){ return(rep(1,m+1))
 }else{
 res=k-sum(2^(0:m))
 return(rep(1,m+1)+as.integer(intToBits(res))[1:(m+1)])

which produces

> sum(deco(2016))
[1] 16
> sum(deco(2017))
[1] 16
> sum(deco(1789))
[1] 18

Le Monde puzzle [#940]

Posted in Kids, Statistics, Travel, University life with tags , , , on November 11, 2016 by xi'an

A sudoku-like Le Monde mathematical puzzle:

On a 3×3 grid, all integers from 1 to 9 are present. Considering all differences between adjacent entries, the value of the grid is the minimum difference. What is the maximum possible value?

In a completely uninspired approach considering random permutations on {1,..,9}, the grid value can be computed as

neigh=c(1,2,4,5,7,8,1,4,2,5,3,6)
nigh=c(2,3,5,6,8,9,4,7,5,8,6,9)
perm=sample(9)
val<-function(perm){
min(abs(perm[neigh]-perm[nigh]))}

which produces a value of 3 for the maximal value. For a 4×4 grid

neigh=c(1:3,5:7,9:11,13:15,1+4*(0:2),2+4*(0:2),3+4*(0:2),4*(1:3))
nigh=c(2:4,6:8,10:12,14:16,1+4*(1:3),2+4*(1:3),3+4*(1:3),4*(2:4))
perm=sample(16)
val<-function(perm){
min(abs(perm[neigh]-perm[nigh]))}

the code returns 5. For the representation

[,1] [,2] [,3] [,4]
[1,] 8 13 3 11
[2,] 15 4 12 5
[3,] 9 14 6 16
[4,] 2 7 1 10

art brut

Posted in Books, pictures with tags , , , , on November 6, 2016 by xi'an

Le Monde puzzle [#977]

Posted in Books, Kids, pictures, Statistics, Travel, University life with tags , , , , , on October 3, 2016 by xi'an

A mild arithmetic Le Monde mathematical puzzle:

Find the optimal permutation of {1,2,..,15} towards minimising the maximum of sum of all three  consecutive numbers, including the sums of the 14th, 15th, and first numbers, as well as the 15th, 1st and 2nd numbers.

If once again opted for a lazy solution, not even considering simulated annealing!,

parme=sample(15)
max(apply(matrix(c(parme,parme[-1],
parme[1],parme[-(1:2)],parme[1:2]),3),2,sum))

and got the minimal value of 26 for the permutation

14 9 2 15 7 1 11 10 4 12 8 5 13 6 3

Le Monde gave a solution with value 25, though, which is

11 9 7 5 13 8 2 10 14 6 1 12 15 4 3

but there is a genuine mistake in the solution!! This anyway shows that brute force may sometimes fail. (Which sounds like a positive conclusion to failing to find the proper solution! But trying with a simple simulated annealing version did not produce any 25 either…)