April 2020
Intermediate to advanced
344 pages
8h 22m
Japanese
Content preview from Pythonではじめる教師なし学習 ―機械学習の可能性を広げるラベルなしデータの利用
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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.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.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.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.
1.6
教師なし学習アルゴリズムの詳細
15
難しい。この手法の問題点については
7
章でも詳しく述べる。
1.6
教師なし学習アルゴリズムの詳細
ここからは、ラベルがない問題を考えてみよう。教師なし学習アルゴリズムは、予測をするのではな
く、データの背後にある構造を学習しようとする。
1.6.1
次元削減
次元削減（
dimensionality reduction algorithm
）と呼ばれるアルゴリズム群がある。これらのアルゴ
リズムは、あまり関係のない特徴量を捨て、興味深い特徴量を可能な限り維持することで、元の高次
元の入力データを低次元の空間に射影する。次元削減を用いると、教師なし学習
AI
で効率的にパター
ンを発見できるようになり、大規模で計算量の大きい問題（画像、動画、音声、テキストなど）を効率
的に解くことができるようになる。
1.6.1.1
線形射影
次元削減には
2
つの流れがある。
1
つは線形射影で、もう
1
つは非線形次元削減だ。まずは線形射影
から見ていこう。
主成分分析
データの裏にある構造を学習する方法の
1
つとして、特徴量のうちデータの分散を説明するために最
も重要なものを特定する方法がある。すべての特徴量が同じように重要なわけではない。データによっ
て値がほとんど変わらないような特徴量は、データセットを表現する役にはあまり立たない。逆に大き
く値が変わるような特徴量は、データの分割するモデルの役に立つので、詳しく見ていく必要がある。
主成分分析（
PCA
：
Principal Component Analy ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
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.