Which items win games?

For LeagueMath.com's very first post I wanted to start thinking about the correlation between buying certain items and winning. I ended up generating a couple interesting graphs unlike any I've seen elsewhere.

[Disclaimer: This analysis is quick, rough, and for entertainment purposes only. Any resemblance to actual statistical significance is purely coincidental. Any inconvenience or damage stems only from banal incompetence, never malice. Also, I love you.]

I wrote a Javascript program that spiders Riot's match history api starting at a specific summoner and recursively downloads recent ranked solo-queue games by that player, and players that player played with recently, and players they've played with recently, etc. This allowed me to quickly accumulate many many thousands of patch 4.16 matches from around my MMR (high silver.)

For each of those games, I looked at which items each player had at the end of the game. I scored each item positively if it was held by a winner, and negatively if it was held by a loser. I then plotted the items in order by this score. Exciting stuff.

Some parts of this image aren't too surprising. For example, most of the items near the top are expensive. SPOILER ALERT: Having expensive items at the end of the game is correlated with winning.

Though, perhaps it is surprising is that the item at the very top isn't the most expensive, and those Sorcerer's Shoes only cost 775g to upgrade! Also, the items near the bottom might be the ones you'd expect to find there. Homeguards are typically bought by players that are about to lose, and having unused wards, undrank potions, and latent Doran's items is never good. Finishing with un-upgraded boots, a free yellow trinket, and unfinished Warden's Mail items also seems bad.

I did the same analysis with much higher-ranking players. I seeded the scraper with Doublelift to get similar data, but from challenger players who are much better than I at the game.

Things are largely the same in the games with the substantially better players. I do see the upgraded Sweeping Lens much higher in the list. It's a well-known fact that better players manage vision better. The Locket of the Iron Solari climbed as well. Improved presence from support in higher-ranked games, together with better use of activated items can probably explain that. The Bloodthirster is above the Blade of the Ruined King in both lists, interestingly enough.

The total domination of both lists by Last Whisper seems to warrant further investigation.

This was my very first idea at analysis. Feel free to give me feedback. Regardless, I hope you enjoyed this. I know I had a lot of fun programming it. I'm going to post additional analysis regularly here on LeagueMath.com; so I'll be seeing you around.

No summoners were harmed in the making of this page. If you keep playing games to generate data, then I'll keep doing math and we can all have more fun.

Peace.