San Miguel de Allende

Custodia

De O. P.

American Trends

I just found some graphs from a dating website. I suppose that in order to get an account in this matching service you need to answer some questions and this give the data for these graphs. The source is this.

Rate Your Self-Confidence

Does weather explain the map?

Is homosexuality a sin?

The next one is very striking,

Which would you rather lose?

Go to the website where I got these graphs from. They have other cool stuff.

Beta Distribution app

I found this java app by Brendan O'Connor on the different shapes of the beta density for different parameter values. Use the arrows in your keyboard.

Feynman Lectures Online

When I took my first course on physics (against my will) with Prof Leonel Torres I discovered the existence of a famous physicist called Richard Feynman. At that time I was not interested on physics at all. But some things changed later. Indeed I moved to things even less serious than physics :D . Some years later I read one of my favorite books so far: Surely You're Joking Mr Feynman! in which Feynman tells his story to an interviewer and this became later his autobiography.

Feynman is famous among other things because he worked in the Manhattan project. Also he won the Nobel Prize. I recently found that Microsoft Research released a series of lectures at Cornell by Feynman in 1964. They can be found here on Youtube. So far I have watched only the first one. It is about the law of gravitation. The second one is about the relationship between physics and mathematics.

It is so amazing how a science can begin by describing "laws". That is, until there is no experiment that contradicts the law, then it still remains as a law. This is so weak and however it is the most serious method we have as humanity to understand our world. This reminds me Hilbert's problem 6: Can physics be axiomatized? I have never heard of any work on that problem.

The advantage of physics over economics is that the former has lots of predictive power. The latter does not. The predictive power of physics rely on averages. Measurements on physics are not about every single particle in a system, but just on the average that summarize the behavior of all of the particles conforming the system. Macroeconomics has tried to do that without much success.

If you feel more interested on physics than on economics (as most of you are) check these lectures by Walter Lewin from MIT. That's the best class of physics I've known of. He has on videolectures a complete course on classical mechanics and another on electromagnetism. Both of them are wonderful, I've seen almost all the lectures. By the way, once I met a guy that took one of his courses, he said it was pretty difficult but a very good professor.

Insectos

En Tucson hay muchos insectos, son grandes y hay demasiados en el verano. Lo más impresionante son las chicharras (cicadas), dominan la ciudad y hacen ruido desde el medio día hasta el anochecer. Viven en los árboles llamados palo verde y caminar por las calles es como caminar junto a líneas de alta tensión.

Encontrar las chicharras en las ramas de los árboles es difícil, así que no tengo fotos de ellas (son como moscas gigantes). Por ahora solo tengo fotos de unos como escarabajo-cucarachas. Vuelan y tienen antenas fragmentadas. Ya pregunté bien y no son cucarachas ni parientes cercanos. He aquí algunas de ellas, admiren su belleza:




Luego me encontré al oso hormiguero versión insecto:

Luis is a nerd ...

Luis is a nerd and so am I.

The Free-Riders II

As a second part of the previous post, this is the graph of the group contributions and the earnings per period. It is not one of my favorite graphs.


(Click on the image to see larger version)

The Free-Riders

(Click on the image to see larger version)

Tonight in class we did the classical voluntary contributions experiment. The class was divided into 5 teams. Each team had at the beginning of each period 100 tokens. At each period, the teams had to decide independently the amount of tokens to keep for private consumption and the rest of the tokens for the group contribution. Once each team decided how to split the 100 tokens, I collected the group contributions and wrote on the board the sum of those contributions (the teams did not know the amount of contributions from the other teams, just the total). Then each calculated their earnings in that period: earnings=private consumption + 0.7 (total group contribution). The factor 0.7 was arbitrarily chosen and fixed for all teams and all periods. This was repeated 10 times (with 2 periods of training at the beginning). At the very end, each time added up the earnings from each period, this total amount of earnings is the number that is at the right of the graph for each team.

The name of the winning team (notice that there was a team that chose the name "Winners" and they did not win) was switched by me to "The Free-Riders" for obvious reasons.

Notice that the winning team played the optimal strategy from the beginning. No communication was allowed in the experiment between teams, only within the teams.

This is a sample of the sheet each team had,

period	endowment	private exchange*	group exchange*	total group contribution	earnings**
1	100

*These columns must satisfy
Private Exchange + Group Exchange = 100

**To calculate this column use
Earnings = Private Exchange + 0.7 (Total Group Contribution)

Excel Question

I had to do this graph in MatLab since I could not figure out how to do it in Excel.

(Click on the image to see larger version)

Does someone know how to do the same in Excel?

(that is, how to label the dots with another series of data?)