Fangraphs keeps track of the number of pitches a batter sees. So you can easily take that and divide it by plate appearances and see how many pitches a batter is seeing on average.
Barton actually has a fantastic eye and plate approach. He just doesn't have any power.
To those that do not know mathematics it is difficult to get across a feeling as to the beauty, the deepest beauty of baseball. If you want to learn about baseball, to appreciate baseball, it is necessary to understand the language she speaks.