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The post introduces the concepts of entropy and diversity (and cardinality) in the field of biology. While I’m acquainted with the definition of entropy in information theory (and, slightly less, physics), I found really beautiful that those concepts could be applied in a very elegant way in population biology.
The first part applies the entropy definition to a finite probability space, representing an ecosystem with several species. Each probability shows how a particular species is frequent, namely the probability to encounter an indivual of that species. The entropy represent the diversity of the ecosystem, or, in a very rough language, how in “a good state” is the ecosystem.
The second part extends to a finite probability metric space. In this space, the probability has the same meaning as before. The metric distance among the points in the space grasps the idea of how a species is similar to one another. Thus, a low distance between two species means that these two are quite similar.
From the diversity you could derive the entropy and the cardinality of a probability (metric) space.
Intrigued by the post, I wrote a small ruby gem to calculate the entropy, the diversity and the cardinality for a probability space with or without a metric. The gem is on rubygems.org,entropy_gem, and the source code is on github.
I’m wondering if, passing from information theory to population biology to computer science again, these concepts could be applied in the field of machine learning, perhaps in genetic programming or any algorithm inspired by the mechanisms on evolutionary biology.
Tell me if you have any suggestion, comment or correction.
I recently bought a Guide10 Adventure Kit solar panel from Goal0. The kit includes a Nomad7 solar panel and a battery pack with 4 AA NiMh batteries.
Since I needed it in time for the Chaos Communication Camp, and didn’t found a vendor in Europe, this was a good chance to test Borderlinx, a forwarding service that provides you an US address if you live outside USA. So here are my opinions about both the solar panel and the forwarding service.
Goal0 Nomad7 Solar Charger
Pros: The solar panel can charge directly your smarphone or the battery pack. It has an USB 5V output and a 12V output with a standard car charger socket.
The battery pack includes 4 AA NiMh batteries, but you can use any NiMh battery, and an adapter to charge the AAA type. The battery pack can then be used to charge the smartphone by switching it to output mode.
Cons: I wished it had included some adapters, expecially for old phone that require a charger. You can you a car charger, tough, if you have one, but that forces you to use the direct 12V output of the solar panel, instead of the 5V battery pack output.
Bottom line: So far the products seems very good. I used the battery pack to charge my Nexus S, and the solar panel to charge the battery pack, multiple times. The solar panel is water resistant and light, I can recommend it for backpacking/camping.
The service of Borderlinx is operated by DHL. It provides a US address, and as a bonus a UK address. You can use this address as a shipping address when you buy from an online shop. Borderlinx then sends your package to your address.
Pros: Creating an account is quite easy, it doesn’t require a credit card. Borderlinx has a retention period of 30 days, during this time you can accumulate your goods, and then send them in an unique shipping, slightly saving some cents. The service calctulates for you all the shipping cost, duty and taxes, so you know almost exactly what you’re going to pay and you don’t have to deal with duty forms and taxes. It offers standard and express delivery. Plus, most online shops offer free shipping inside US.
Cons: the service isn’t exaclty cheap.
Bottom line: the shipping was fast and the service overall experience was good, but not cheap. I think it can be used to buy things that you can’t’ find in your country (but beware that some US vendors don’t ship to addresses provided by services like Borderlinx), but for a more casual shopping you should evaluate with attention the cost and whether it is worth.
The good news is that the wisdom of crowds exists. When groups of people are asked a difficult question—say, to estimate the number of marbles in a jar, or the murder rate of New York City—their mistakes tend to cancel each other out. As a result, the average answer is often surprisingly accurate.
But here’s the bad news: The wisdom of crowds turns out to be an incredibly fragile phenomenon. It doesn’t take much for the smart group to become a dumb herd. Worse, a new study by Swiss scientists suggests that the interconnectedness of modern life might be making it even harder to benefit from our collective intelligence.[…]
This week marks 50 years since Yuri Gagarin climbed into his space ship and was launched into space. It took him just 108 minutes to orbit Earth and he returned as the World’s very first space man.
To mark this historic flight we have teamed up with the astronauts onboard the International Space Station to film a new view of what Yuri would have seen as he travelled around the planet.
Weaving these new views together with historic voice recordings from Yuri’s flight and an original score by composer Philip Sheppard, we have created a spellbinding film to share with people around the World on this historic anniversary.
Late as usual, I remember the first human in orbit around the Earth.
I’m a newbye runner. Last winter I started the C25k program and now I’m able to steadily run 5 km (I won’t disclose the time though☺), so I searched for an Android App to record the time spent, the route I took and a few other stats.
After a brief search I restricted the set of candidates to three applications, namely Cardiotrainer, Endomondo and Runkeeper Pro, and tried them all. The first two are available in the Android Market both as a free version and as paid enhanced version (I bougth them both and here I’m evaluating the paid version); the last one is free.
Here are a few pros and cons I found for each app:
- the app has probably more features than the other two;
- stable, easy to use;
- good autopause if you stop during your workout;
- integrated with other applications to check the progress of your weight, if you want to decrease it, and to log the calorie intake of your meals.
- I don’t like the website where you upload your workouts. It has a small number of statistics and features;
- it’s the most expensive, but with the paid version you get any of the other integrated apps for free (race module, weight progress, etc.);
- you can’t set a goal for a workout, except in the race mode, but after the race completes it stops to record the workout.
- the website has a good number of stats and featurs, and a sort of “social” twist. You can share your workouts with friends, comment on others’ workouts, and so on
- stable, easy to use;
- you can set a goal for a workout (time or distance);
- you can control the app with the headset (I’ve not yet tried that);
- developed by a european crew, it’s the only one that distinguishes between cycling as a sport and cycling as transportation☺.
- you can’t vary the notification interval during the workout, it’s fixed on every km;
- the autopause sometimes fires even if you’re running. I suspect it has something to do with GPS tracking.
- it has the most useful set of features for runners: notification for time and distance (and both active at the same time), with configurable interval;
- you can edit the workout and modify it, thus for example you can set a goal of 30 min run with 5 min slow, 5 min fast, etc, and choose the number of repetitions;
- good website, I specially like the possibility of finding local users of the app in your zone. Has a fair set of stats and you can dowload predefined training programs to your app, albeit not for free.
- The app is free, but you can download some training programs or access all your stats only with a monthly fee; I prefer paying for the app, even a not small amount as for the Cardiotrainer App, instead of paying a monthly fee.
- no autopause.
And the winner is…
The Cardiotrainer was the first app I installed, since at first glance seemed the most used. Now I appreciate the stats you can collect on your workouts on Endomondo’s and Runkeepers’ websites. You can easily switch from one app to another, for all three apps support the import/export of workouts in gpx format.
I suspect the Runkeeper it’s the most useful if you’re a serious runner, but Endomondo comes pretty close. Right now I chose to use Endomondo.