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PageRank Algorithm Applied To the Food Web
An anonymous reader brings word of a new application for PageRank, Google's link analysis algorithm: monitoring the food web in an ecosystem. A team of researchers found that a modified version of PageRank can predict with great accuracy which species are vital to the existence of others. Quoting:
"Every species is embedded in a complex network of relationships with others. A single extinction can cascade into the loss of seemingly unrelated species. Investigating when this might happen using more conventional methods is complicated, as even in simple ecosystems, the number of combinations exceeds the number of atoms in the universe. So, it would be impossible to try them all. Co-author Dr. Stefano Allesina realized he could apply PageRank to the problem when he stumbled across an article in a journal of applied mathematics describing the Google algorithm. 'First of all, we had to reverse the definition of the algorithm. In PageRank, a web page is important if important pages point to it. In our approach, a species is important if it points to important species.'"
Pagerank is just a repeated application of a transformation matrix. It has the effect of running a Markov model (a way to model discrete states) until there is convergence. He just used a Markov model the way that it is supposed to be used...
I dont get it... what's notable here?
What factorial does it take to equal that number? I know that its very easy in math to get numbers that large, but this wasn't a place I expected to find it.
FanFictionRecs.net
Looks like you're a colossal failure
they didn't use Pigeon Rank on the food web.
A species is more important if it points to my stomach.
Also see my upcoming research topic:
Bioinformatic Algorithm for Standard Texan-Americans with Retro-Dissonant Suppositions
I expect to prove that BASTARDS are essential to the American way of life.
In some respect, an economy can be considered as a sort of ecology. If this research holds up, it would be interesting to do the same sort of analysis to rank the importance of industries and occupations. Which ones are necessary and vital and which ones (MPAA?) can be discarded without harm or even with benefit to the rest of the ecology.
And why?
We are humans. Really humans are the only species that in the end matter. So long as we have enough food and oxygen, all is good and the survival of our species is guaranteed (assuming no effects of huge disasters such as an asteroid impact, etc.)
Taxation is legalized theft, no more, no less.
In PageRank, a web page is important if important pages point to it. In our approach, a species is important if it points to important species.'"
The difference is, its pretty obvious to a human if a page is important. On the other hand there are a lot of species that we don't know if they are important or not. So how do we know what the "important" species are? Other than humans, we don't know of any real "important" species. Could the ecosystem survive without X? Theres no way we can really know that.
Taxation is legalized theft, no more, no less.
I've often been annoyed by the excessive focus on the iconic and popular species in many endangered species awareness campaigns. It is easy to say "we are spending a million dollars on protecting a worm?" in Congress, but when more renowned species like a hammerhead shark variety are endangered, they will naturally get more attention. Now scientists can defend their case for funding by pointing to this algorithm.
I'm guessing you've never watched 'Silent Running', but given what you said you might wanna start your re-education with another old movie: 'Soylent Green'.
As long as the world is this overpopulated we'll always have enough food. Cannibals aren't bad people, they're just pragmatic.
Please tell how you think we are currently becoming overpopulated? For one we have enough food to feed -everyone- the problem is corrupt government and lack of education that causes hunger in third-world countries. In first world countries its quite easy to get food and shelter so no one should ever die of hunger. Yeah, you won't be eating steak and shrimp every night, but you aren't going to starve to death. Take a drive to North Dakota sometime if you don't think we have enough space. If you read the UN's projections for birth rates (http://www.un.org/esa/population/publications/wpp2006/WPP2006_Highlights_rev.pdf) it shows a -sharp- decline in birth rates for most of the developed world. And in general a "bubble" of population increase then a decrease (because there is a large amount of old people who are going to die). Even a doubling in human population isn't really a huge deal with increasing technology leading to increased crop yields and the ability to farm previously unfarmable areas. And we have way more than enough space.
Taxation is legalized theft, no more, no less.
I'm guessing you've never watched 'Silent Running', but given what you said you might wanna start your re-education with another old movie: 'Soylent Green'.
I think you need to re-educate yourself with another movie: The Omega Man. If that's where we'll end up anyways, who cares how we get there? Eat drink and be merry, I say. Isn't there some movie about people being brainwashed with media and living in a world that isn't real (but they think it is) because they're too plugged into modern culture to know the difference? I mean, if hollywood is providing you with all your examples, you'd best take the good with the bad.
Have you learned nothing from history? We can know if an ecosystem survives without certain members.
It just isn't a good idea to experiment.
That's interesting, because most americans don't care about preservation.
My proof?
Wal-mart (and the associated industries that support low prices).
Sure, save the whales/sharks/pandas/worms. But I better get my tampico for 0.34$/bottle and jeans for $4.99 so I can afford to help out.
I would have thought that an animal-based algorithm such as PigeonRank would be more applicable to this problem.
The World Wide Web is dying. Soon, we shall have only the Internet.
If you're under 40 and in good health you're in for a rather rude awakening, with those beliefs. You'll likely live to see the shit begin to hit the fan in a serious way. Google and other online sources should be education enough for you. I'm too disorganized to do anything more than plant the seed; you'll have to water and feed it.
In the context of being an important part of the web, what is the page rank for the species homo sapiens?
Did you even read the fine summary? It does not rank the food we eat everyday (well, at least not directly). It is to determine the importance of each species so that we can better spend our effort in preserving them. This has the helpful effect of keeping ecosystems intact.
I am not new here, and I know a fair amount of people here don't RTFA but seriously, do you people now just read the headlines and start making useless comments?
Most of us know (or at least believe with a good likelihood of being correct) that our current use (abuse) of fossil fuels is changing the planet in ways that will make it a more difficult place for humans live. You would think that those with children and grandchildren would be the most aware of this, however, this set seems to be the ones who take the most delight in SUV's and vacation flights across the world. Presumably this is the same group that recognizes the dangers of using cell-phones while driving on an intellectual basis, but continues to use them.
So lets see here, I'm supposed to believe some random person on the internet because of A) Sci-Fi films, B) "facts" that contradict reputable sources such as the United Nations and C) ideas that don't make much sense. Lets see here, we have technology that allows us to grow more crops in a single area than ever before, technology that lets us grow more crops with less effort (we have less humans employed as farmers than before yet have more crops than before) and technology that will let us grow crops in places that could never have had crops planted before. We similarly have lots of habitable space, more than ever before. Someone could live in the middle of the desert, yet still have food, a habitable place to live and water.
So in the end, we have more food than we know what to do with, technology enabling us if there was some kind of food shortage to grow our own food in our basements if need be, no shortage of space, etc. Seriously, part of science fiction is... fiction. If it was true, well perhaps I should start carving Ego in big letters in rocks in case humanity forgets about individuality and the word I (for those not in the know this is a reference to Ayn Rand's book Anthem). But really take a look at http://en.wikipedia.org/wiki/File:Population_growth_rate_world.PNG -large- portions of the world have a negative birth rate. So with no science to back up your claims, other than a few science fiction movies, why should I believe you?
Taxation is legalized theft, no more, no less.
Do you have a point? Or did you just use the mention of the term "Pagerank" to come in here and randomly slag off Google?
"A great democracy must be progressive or it will soon cease to be a great democracy." --Theodore Roosevelt
Do you have a point? Or did you just use the mention of the term "Pagerank" to come in here and randomly slag off Google?
The poster has a point, and is certainly not slagging off Google.
The point is that the mathematics of Page Rank is not very deep. A fact which can be asserted.
So let's see here, I'm supposed to believe some random person on the internet A) pooh-poohing science fiction (irony piled on top of irony here), B) who considers the UN to be a "reputable" source (I suppose it is for cases of "reputable" such that "reputable is equal to as least as credible as a huckster selling snake oil"), both of which are C) ideas that don't make much sense.
Good luck growing food in your basement if there is a food shortage serious enough to require people to grow food in their basements. Maybe you can get a few crops in when you're not otherwise engaged in keeping the looters out as they try to see if there's anything to eat in your house.
P.S. The UN and Ayn Rand probably don't mix too well. The only place for ego in world government will be in the leadership. "Individuality" and "I" will be about as much use for those who are not in charge as they are for chickens in an industrial hen house.
The pagerank algorithm is better understood as a kind of Eigenvector Centrality Measure.
See http://en.wikipedia.org/wiki/Eigenvector_centrality#Eigenvector_centrality
Meaning it is not new as a method by itself, but applying it to the linking-structure of the WWW in order to produce
relevant documents for a query, was new. I think it is fair to say that the Google Pagerank matters very little, outside of being able to rank otherwise
not-comparable search results.
And so it is better to state that "a specialized Eigenvector Centrality Measure can predict with great accuracy which species are vital to the existence of others" instead of "a modified version of PageRank can predict with great accuracy which species are vital to the existence of others". One can see that also when one realizes that these biologists have no query, no search, no equivalent of search keywords.
On the other hand, when the post says "Co-author Dr. Stefano Allesina realized he could apply PageRank to the problem when he stumbled across an article in a journal of applied mathematics describing the Google algorithm." -- I guess he might have found the method through the Google name.
Stephan
http://stephan.sugarmotor.org
I'd expect McDonald's to be ranked very high based on importance to the diets of people around the world while the importance of, say, filet mignon to be comparatively negligible. There are times where a popularity contest works: "Hey, people are getting fat. What food should we make healthier? Well, people seem to be eating a lot of hamburgers, so lets see if we can make those leaner!"
Pagerank isn't an important algorithm, it's an application of an important mathematical concept. Pagerank is just computing the limiting distribution of a specially constructed Markov chain, which is very important and has many applications beyond pagerank and 'popularity contests.'
Awesome, now we know which species we can let go extinct!
Property is theft.
Do you have a point? Or did you just use the mention of the term "Pagerank" to come in here and randomly slag off Google?
Apparently the point - that pagerank stinks and is not something I want to pay attention to if used to rank food - was too subtle for you. I don't know if you're a Google employee or just a run of the mill sock puppet but I did not go into a tirade about Google teh company so stop trolling.
These posts express my own personal views, not those of my employer
At the heart of Pagerank is the idea that, if one has a connection matrix between 'things' and these connections are related to the scoree, one can pose the problem as an eigenvalue problem. That's a pretty cool insight, and is applicable to many more fields than internet searches, for instance: ranking articles due to citations, teams based on wins and losses, and now finding important species based on their genetic connections.
I would imagine that the many places Pagerank has found application would count for something when you figure the significance.
Languages aren't inherently fast -- implementations are efficient
To paraphrase Thomas Hobbes: You're a winner or you're dinner.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
NO SHIT!
That is the whole damn point of this analysis, to determine popular food chains between all the animals to see the ones that would cause the largest impact in all the species.
If McDonalds suddenly died, the reverberations it would cause in the human food chain would be crazy!
Yes, the humans will just start targeting Burger King more, but they will end up going through a horrible time as well as they are filled to capacity and end up running out of stock quicker.
By the time they gather enough monies to either build new buildings or buy more stock, a significant amount of their regular customers would probably be pissed off by them running out of stock so much.
Pizza hut doesn't even come in to the argument, it is already dead. (in your average MKer or BKer, "pizzas, ewck")
Sure, "fine dining" might gain some popularity, but it would be very low percentage, like less than 10% increase on average.
There is absolutely nothing wrong with using what is basically a popularity algorithm to determine links like this.
But i can certainly see your criticism since it doesn't show the most information when it comes to how important a species is.
It could be improved to the point where it isn't so much as a food chain, but a verb chain, THIS would be a million times more useful, there are many verbs that animals do that can heavily influence other species, like bees as the best example i can think of.
Also, i hate DFDs...
This could be used to predict which projects are essential to open source and free software.
Certainly this is an additional tool that can be used to explore Lovelock's Gaia hypothesis. If other elements were included in the web of interactions such as atmospheric and dissolved CO2, the actions of rocks it might provide a further insight into global warming and what we should be looking at the mitigate it.
Where do you think low prices come from? Minimum wage in countries like china is pennies a day. Exploitation, really. And encouraging exploitation of people leads to exploitation of other resources. I think there is a hole in your thinking. Or maybe you've never thought about why walmart can sell things so cheap.
This has to be a troll right ?
Seriously, "so long as we have enough food and oxygen, all is good" ? Where the fuck does that food come from, idiot ? What processes combine to create that food ? Which lifeforms are necessary to provide those processes ? Which out of the millions of bacteria is it safe to eliminate before we are unable to digest food at all ?
I suppose you think fossil fuels are good because they are effectively free, all you have to do is dig them up. And that is relevant, as without fossil fuels, there is not enough energy on the planet to sustain our current food supply. We are using stored solar energy to grow food more quickly than nature can alone. When that stored energy runs out, we'd better have a new source lined up or a large number of people will starve.
But apparently we don't need other life forms at all. Instead of pesky insects eating plants or each other, we'll just eat plants or each other. Except there will be no plants without other forms of life to pollinate, spread seeds, provide nutrients and generally be part of the whole process.
I am a representative of an important species and if I point to a web page it becomes important?
How long do I have to point at a certain page to put it on top of Google search results.
Corrected that for you
Living is more than not starving.
Great minds think alike; fools seldom differ.
The *only* thing worthy of note with PageRank is the humongous size of the graph that is being modeled. This could never have been attempted until the 1990's because computers weren't powerful enough before (and the few that were just weren't going to be used for "silly" things like web search).
So what happens when this algorithm determines humans are the least important species to the ecosystem?
Guess who actually got modded as Troll, though? Nope, not the "idiot"... it was my original comment pointing out the larger context being ignored (for the sake of TOFA). Modded as Troll not just once, but repeatedly.
If there's one thing about Slashdot that should change, it's the removal of anonymity when people moderate.
<eyeroll />
Ok, Captain Expert. Pagerank is awful, and that's why Google is not useful to anyone. And these people trying to apply it to what organisms eat other organisms -- not, as you seem to think, to what restaurants are better than others -- is completely moronic as well, since the quality of the organisms' meals are more important than what organisms depend on what other organisms and to what extent, which these poor mislead people are paying attention to.
In short, gosh, I guess I'm the troll and you're the poor victim. Gee whiz, sorry for tricking you like that.
"A great democracy must be progressive or it will soon cease to be a great democracy." --Theodore Roosevelt