Finding Waldo, a flag on the moon and multiple choice tests, with R by Arthur Charpentier.
From the post:
I have to admit, first, that finding Waldo has been a difficult task. And I did not succeed. Neither could I correctly spot his shirt (because actually, it was what I was looking for). You know, that red-and-white striped shirt. I guess it should have been possible to look for Waldo’s face (assuming that his face does not change) but I still have problems with size factor (and resolution issues too). The problem is not that simple. At the http://mlsp2009.conwiz.dk/ conference, a price was offered for writing an algorithm in Matlab. And one can even find Mathematica codes online. But most of the those algorithms are based on the idea that we look for similarities with Waldo’s face, as described in problem 3 on http://www1.cs.columbia.edu/~blake/‘s webpage. You can find papers on that problem, e.g. Friencly & Kwan (2009) (based on statistical techniques, but Waldo is here a pretext to discuss other issues actually), or more recently (but more complex) Garg et al. (2011) on matching people in images of crowds.
Not sure how often you will want to find Waldo but then you may not be looking for Waldo.
Tipped off to this post by Simply Statistics.