Those three stats (K%, BB%, BB/K) are the bulk of what is used to determine a player’s plate discipline, but there are actually quite a few more advanced stats that can be used get a much deeper look into a player’s approach at the plate. It’s really not necessary to get very in-depth with these stats, but a simple description and league context is really all you need to be able to apply them.
In baseball statistics, on-base percentage (OBP; sometimes referred to as on-base average/OBA, as the statistic is rarely presented as a true percentage) is a statistic generally measuring how frequently a batter reaches base. Specifically, it records the ratio of the batter's times-on-base (TOB) (the sum of hits, walks, and times hit by pitch) to their number of plate appearances. It first became an official MLB statistic in 1984.
Another very common stat used to measure plate discipline is a player’s walk-to-strikeout-rate (or BB/K). This is again a fairly straight forward stat, and it is measured simply by dividing a player’s walk total into their strikeout total. The result gives you the average number of times a player walks between each strikeout. So if a player had a BB/K of an even 1.00, that would mean that they walked just as often as they struck-out (which is exceptionally good plate discipline).
In baseball statistics, on-base percentage (OBP) is a measure of how often a batter reaches base for any reason other than a fielding error, fielder's choice, dropped or uncaught third strike, fielder's obstruction, or catcher's interference. OBP is calculated in Major League Baseball (MLB) by dividing the sum of hits, walks, and times hit by a pitch by the sum of at-bats, walks, times hit by pitch and sacrifice flies. A hitter with a .400 on-base percentage is considered to be great and rare; only 55 players in MLB history with at least 3,000 career plate appearances (PA) have maintained such an OBP. Left fielder Ted Williams, who played 19 seasons for the Boston Red Sox, has the highest career on-base percentage, .4817, in MLB history. Williams led the American League (AL) in on-base percentage in twelve seasons, the most such seasons for any player in the major leagues. Barry Bonds led the National League (NL) in ten seasons, a NL record. Williams also posted the then-highest single-season on-base percentage of .5528 in 1941, a record that stood for 61 years until Bonds broke it with a .5817 OBP in 2002. Bonds broke his own record in 2004, setting the current single-season mark of .6094.
In cricket, a player's batting average is the total number of runs they have scored divided by the number of times they have been out. Since the number of runs a player scores and how often they get out are primarily measures of their own playing ability, and largely independent of their teammates, batting average is a good metric for an individual player's skill as a batter.