May 2020
Intermediate to advanced
456 pages
9h 13m
Japanese
Content preview from ゼロからはじめるデータサイエンス 第2版 ―Pythonで学ぶ基本と実践
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16.5
サポートベクタマシン
■
229
16.5
サポートベクタマシン
dot(beta,
x_i)
が
0
となった点の集合は、分類の境界を示しています。我々のモデ
ルがどのように判断したかを正確に表すために、この境界をグラフにしてみましょう
（図16-5）。
ロジスティック回帰の決定境界
有料
無料
使用年数
図16-5 決定境界で分割した有料ユーザと無料ユーザ
この境界は有料と予測したパラメータと無料と予測したパラメータを分割する超平
面です。最も尤度の高いロジスティックモデルを探す過程の副作用としてこの境界を
見つけました。
分類を行う別のアプローチが、学習用のデータを最もうまく分割する超平面を見つ
けることにです。これがサポートベクタマシンのアイディアであり、それぞれの分類と
なるデータからの距離を最大化する超平面を求めます（図16-6）。
230
■
16
章 ロジスティック回帰
超平面による分割
図16-6 超平面による分割
このような超平面を求めるのは最適化の問題であり、我々にとっては高度すぎる手
法を必要とします。またこのように分割する超平面が全く存在しないかもしれないと
いう点も問題となります。これを我々の問題である「誰が有料アカウントを使うのか」
にあてはめると、有料ユーザと無料ユーザを分かつ完全な境界線が存在 ...
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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.