## Maths can reveal true soccer stars

June 17th, 2010 - 6:40 pm ICT by ANI

Washington, June 17 (ANI): Can you ever give statistics on how a soccer player has contributed to a match? Well, a professor at Northwestern University has done just that.

Luis Amaral, combined his love of soccer with his research team’s computational skills to measure and rank the success of soccer players based on an objective measure of performance instead of opinion.

Through their analysis, they could objectively rank the performances of all the players in the 2008 European Cup tournament.

Their results closely matched the general consensus of sports reporters who covered the matches as well as the team of experts, coaches and managers that subjectively chose players for the “best of” tournament teams.

“In soccer there are relatively few big things that can be counted. You can count how many goals someone scores, but if a player scores two goals in a match, that’s amazing. You can really only divide two or three goals or two or three assists among, potentially, eleven players. Most of the players will have nothing to quantify their performance at the end of the match,” said Amaral.

To find a quantitative way to rank players, co-author and Northwestern graduate student Josh Waitzman first wrote software to pull play-by-play statistical information from the 2008 Euro Cup website.

This type of extensive statistical information is usually only gathered for important matches, said Amaral.

The researchers used the data to quantify the performance of players by generalizing methods from social network analysis.

“You can define a network in which the elements of the network are your players. Then you have connections between the players if they make passes from one to another. Also, because their goal is to score, you can include another element in this network, which is the goal,” said Amaral.

The researchers mapped out the flow of the soccer ball between players in the network as well as shooting information and analyzed the results.

“We looked at the way in which the ball can travel and finish on a shot. The more ways a team has for a ball to travel and finish on a shot, the better that team is. And, the more times the ball goes through a given player to finish in a shot, the better that player performed,” said Amaral.

“It would never happen by chance that we would get such striking agreement with the consensus opinion of so many experts if our measure wasn’t good,” he added.

He said that this kind of analysis can be used outside of the soccer world, too. Companies could use the method to rank and evaluate the performance of employees working together on a team project, for example.

The results of the study are published in PLoS ONE. (ANI)

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