PDF Publication Title:
Text from PDF Page: 034
6.2 Food Webs Allesina and Pascual (2009) used the PageRank algorithm to measure species relative importance for co-extinction. In their 2009 paper, Allesina and Pas- cual sought to analyze complex ecological networks in an attempt to determine the importance of individual species in the food web. A food web can be cre- ated by taking nodes as different species in the environment and the directed edges as the transfer of energy from one species to another, most often by being eaten. One difference between this and the basic PageRank is that importance is flipped, so that a species is important if it points to, or in other words is eaten by, an important species. Food webs are also do not make an irreducible matrix, but a damping factor is unrealistic, since food cannot randomly ”jump” around a food web. Allesina and Pascual (2009) dealt with this by adding a special node, a ”root,” which stood for the food source of all of the primary producers in the food web. Every node also had a link from itself to the root, which signified the intrinsic loss of matter of a species, which builds into detritus and is recy- cled into the food web. By applying these modifications, the food web becomes irreducible. For testing, Allesina and Pascual (2009) performed in-silico extinction ex- periments. Each step Allesina and Pascual (2009) removed a single species and recorded the number of secondary extinctions. There were several algo- rithms used to determine the species removed. The PageRank algorithm was used to remove the species with the highest PageRank at each step. Allesina and Pascual (2009) also measured the effects of the removal of the species with the highest number of connections, and the removal of species according to their closeness centrality, where nodes are considered highly central if they have a short distance to many nodes. Also measured was the betweenness centrality, where a node has high betweenness if it lies on the shortest path of 29PDF Image | MATHEMATICS BEHIND GOOGLE PAGERANK ALGORITHM
PDF Search Title:
MATHEMATICS BEHIND GOOGLE PAGERANK ALGORITHMOriginal File Name Searched:
MOOR-THESIS-2018.pdfDIY PDF Search: Google It | Yahoo | Bing
Cruise Ship Reviews | Luxury Resort | Jet | Yacht | and Travel Tech More Info
Cruising Review Topics and Articles More Info
Software based on Filemaker for the travel industry More Info
The Burgenstock Resort: Reviews on CruisingReview website... More Info
Resort Reviews: World Class resorts... More Info
The Riffelalp Resort: Reviews on CruisingReview website... More Info
CONTACT TEL: 608-238-6001 Email: greg@cruisingreview.com (Standard Web Page)