The Player Barometer explained

What is it?
The UEFA EURO 2016 Player Barometer tracks players' form in the build-up to and during the tournament. The Barometer runs official player statistics through a specially designed algorithm to create rankings based on player performances.

Player data from qualifying formed the initial basis for the rankings, which have taken into account performances for club and country from 1 January 2016. This gives a unique and comprehensive evaluation of players' form when UEFA EURO 2016 kicks off, after which the Barometer will track which players are excelling in the tournament itself.

How it works
All players are assigned a primary position for which they are expected to play the majority of the time. 

The player categories are defined as: goalkeepers, full-backs, central defenders, defensive midfielders, central midfielders, attacking midfielders, wingers and forwards.

The data considered for each player is specific to the position type. For example, tackles and interceptions are considered to be key statistics for defensive midfielders, while successful dribbles and crosses are core stats for wingers.

The algorithm uses player stats from all matches, club and national team, and updates after these matches are played. During UEFA EURO 2016, the rankings will update during every match.

Weighting
As the Barometer acts as a form tracker, the more recent the match, the higher the weighting assigned to the data from it i.e. player stats from yesterday are given more significance than those from last week. If a player is not active (e.g. due to injury or non-selection), his ranking will decrease over that period of inactivity.

Additional weighting is attributed for quality of opposition using UEFA coefficients as the foundation of the values.

Once UEFA EURO 2016 starts, statistical events (e.g. goals, assists, tackles, saves) for the 552 players will be given a significantly higher weighting to maintain an accurate ranking of those performing well in France.