17Nov/16

Where’s Waldo? Here he is!


Yesterday, I came across a nice article untitled “Here’s Waldo: Computing the optimal search strategy for finding Waldo“, written by Randal S. Olson. I used the data he shared to apply a correction to the kernel density estimation of Waldo’s location.

In this article, Randal explains that he has devoted some time to try to compute the optimal search strategy for finding Waldo. To that end, he has used some machine learning techniques.
From an image provided by Slate (Here’s Waldo, 2013, by Ben Blatt), Randal S. Olson retrieved the coordinates of 68 different locations of Waldo, and kindly shared the data afterwards.

[…]

03Nov/14

French dates in R – From Mac OS to Windows

Station Clock - By derivative work: FischX (talk) Station_Clock.jpg: User:JuergenG, User:AlMare (Station_Clock.jpg) [CC-BY-SA-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0) or CC-BY-SA-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons
The other day during my R lecture, something I did not expect happen… I should have known, or at least guess that it would not work… But I wanted to believe it would. When I gave examples on how to read both English and French formatted dates in R, what was working perfectly on Mac OS X did not on Windows Seven. The example was the following:

d_char_fr <- "Mer 04 Fév 2015"
d_char <- "Wed 04 Feb 2015"
as.Date(d_char_fr, format = c("%a %d %b %Y"))
as.Date(d_char, format = c("%a %d %b %Y"))
30Oct/14

Coordinates of “hot-spots”


Last week I uploaded a note about the paper @freakonometrics and I have submitted again after we added quite a few revisions. We have already made available most of the R code to reproduce our applications (on this GitHub repository). However, we did not share our method to obtain the coordinates of the “hot-spots” areas

14Feb/14

Closest distance between countries

We sometimes need the distance between two countries in econometric models, for instance in gravity models. Bur for some countries, I think this measure could cause problem. Let’s take an example. If we want to model the volume of trade between country (i) and country (j), the economic theory says it will depend on the distance between (i) and (j). Let (i) be China, (j_1) Japan, and (j_2) India. The distance between (i) and (j_1) will be lower than between (i) and (j_2). Can we consider, though, that Japan is farther from China than India is?

So, rather than compute the distance between two head cities, it might be more accurate to compute the closest distance between the borders. If a border is shared by country (i) and country (j), then the distance should be zero.