Starting next month, I hope to add two sets of stats to my usage statistics thread: teammates (which Pokemon are most often paired with a given Pokemon on a team) and checks and counters. Teammates is extremely straightforward (two Pokemon are either on the same team or they're not). But how do you define a check or a counter? Well let's start by talking about the data we have access to. On its initial pass, my PO/PS log reader records information about the Pokemon that were present in the battle, but also the results of each and every matchup between two Pokemon. So consider this example battle: Alice leads with Ferrothorn, Bob leads with Infernape. Alice pulls back Ferrothorn and sends out Heatran. Bob predicts that and uses Close Combat to KO. Alice sends out Gigalith. Bob uses Close Combat again, but Alice's Gigalith survives with Sturdy and goes for Explosion, taking out both Pokemon. Alice sends out Ferrothorn, Bob sends out Starmie. Alice switches Ferrothorn out for Lanturn while Bob switches Starmie out for Bouffalant. Alice has Lanturn use Volt Switch, swapping out Lanturn for Ferrothorn. Bouffalant attacks, not doing much to Ferrothorn. After incurring quite a bit of damage, Alice's Ferrothorn manages to KO Bouffalant. Bob sends out Scizor and takes out Ferrothorn with a U-Turn, sending Starmie out at the end of the turn. Alice's Starmie attacks Lanturn, activating Lanturn's Red Card and dragging out Scizor. Bob resigns. My log reader would parse that battle into the following summary: Ferrothorn vs. Infernape: Ferrothorn was switched out Heatran vs. Infernape: Heatran was KOed Gigalith vs. Infernape: double down Ferrothorn vs. Starmie: double switch Bouffalant vs. Lanturn: Lanturn was switched out Bouffalant vs. Ferrothorn: Bouffalant was KOed Ferrothorn vs. Scizor: Ferrothorn was u-turn KOed Lanturn vs. Starmie: Starmie was forced out Note that the ordering of the "x vs. y" is alphabetical, not by player. Also note the different types of ways a matchup can end: double down: both Pokemon are fainted by the end of the turn double switch: whether by u-turn or by actual switch, both Pokemon are replaced by the end of the turn one Pokemon can be switched out one Pokemon can be KOed one Pokemon can KO the other while switching out (via U-Turn) one Pokemon can be forced out by Red Card, Roar, etc. So at the end of the month, after parsing hundreds of thousands of logs, we end up with a matrix of data telling us what happens whenever Pokemon x faces off against Pokemon y. The question is, how do we use this data to determine who is the best counter or check for a given Pokemon? But, BEFORE WE ANSWER THAT QUESTION, I have a much more fundamental question, which I want answered FIRST: What is a check, and what is a counter? And how are they different?