Player: Position Groupings
CTG groups players into 5 position groupings which more naturally fit how players play in today's NBA. They are: point, combo, wing, forward, and big.
A point is someone who primarily plays point guard.
A combo splits time between point guard and shooting guard.
A wing splits time between shooting guard and small forward, or exclusively plays one of those two positions.
A forward splits time between small forward and power forward.
A big primarily plays either power forward or center or splits time between the two.
The Gritty Details
These position groupings are calculated for each player on a per-season basis. If a player switches teams mid-season, they can have separate groupings for each team they played on. The groupings are calculated by attempting to put all players on a team in order of "most point guard-like" to "most big man-like", and then looking at each lineup the team played in that year and ordering the players accordingly. From that we can estimate what position a player was playing in any given lineup and see what percentage of minutes the player spent at any given position. For example, we estimate that in his second season, CJ McCollum played just 2% of his minutes at PG, 93% at SG and 5% at SF. But in his third season we estimate he played 34% of his minutes at PG and 66% of his minutes at SG.
From there we define a player's primary and secondary positions. A primary position is whatever the player played most. A secondary position is whatever position the player played second-most, as long as it represented more than 10% of his total minutes played. So in the McCollum example, he would have a primary position of SG and no secondary position in his sophomore season, but a primary position of SG and a secondary position of PG in his third year.
We then simply use the above definitions to put players into the appropriate groupings. In McCollum's case, he would be a wing in his sophomore season and a combo in his third.