October 2014
Intermediate to advanced
288 pages
6h 27m
Japanese
Content preview from 実践 機械学習システム
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160
8
章 回帰：レコメンドの改良
8.1.1
二値行列を用いたレコメンド
Netflix Challengeのコンテストを通じて、参加者は多くを学びましたが、特に次のことは興味深い
教訓になりました。それは、どの映画に点数を付けたかを知ることだけで、そのスコアは知らなくて
も、ユーザに対してかなり多くのことを知ることがきる、ということです。このことは今考えると当た
り前のように感じますが、コンテストが行われている時は明確に意識されていませんでした。
ユーザが点数を付けた映画を1、点数を付けていない映画を0とする二値行列を用いるだけでも、有
用な予測を行うことができます。今考えると、これは全くその通りです。私たちはランダムに観たい映
画を選ぶのではなく、これまでの経験から自分が好きそうな映画を選びます。それと同じで、レビュー
として点数を付ける映画をランダムで決めるのではなく、印象に残っている映画に対してだけ点数をつ
けていることが多いでしょ
う（もちろん例外はありますが、このことは全体としては正しいでしょう）。
私たちは行列を画像として可視化することができます。行列の値（映画の点数）は小さい四角形で描
画し、四角形の色が黒い時、それは点数が付けられていないことを意味し、白になるに従って点数が
高くなることを意味します。行列を可視化することで、ほとんどの領域が黒の場合、それは疎行列で
あることが一目でわかります。また、あるユーザは他のユーザよりも多くの映画に点数を付けているこ
ともわかりますし、ある映画は多 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.