August 2015
Intermediate to advanced
312 pages
7h 28m
Japanese
Content preview from 初めてのSpark
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224
11 章 MLlib を使った機械学習
11-1
最後に、ほとんどの学習アルゴリズムには、結果に影響を及ぼすパラメータが複数あるので、実
際に利用されるパイプラインは、複数バージョンのモデルをトレーニングし、それぞれをする
ことになります。そのためには、一般的に入力データを「トレーニング」セットと「テスト」セッ
トに分け、トレーニングは前者でのみ行い、モデルがトレーニングデータに対してしていな
いかを調べるためにテストセットを利用できるようにします。
MLlib
には、モデル評価のためのア
ルゴリズムが複数用意されています。
11.3.1
ンル：ムの分類
MLlib
の手短なサンプルとして、スパムの分類器を構築するためのきわめてシンプルなプログ
ラムを紹介しましょう（
11-1
から
11-3
）。このプログラムでは、
MLlib
のアルゴリ
ズムを
2
つ使用しています。
HashingTF
は、という特徴ベクトルをテキストデー
タから抽出し、
LogisticRegressionWithSGD
は、ロジスティック回帰手続きを、確率的勾配降下法
（
Stochastic Gradient Descent = SGD
）を使って実装しています。ここでは、
spam.txt
と
normal.
txt
という
2
つのファイルから始めることにしましょう。これらのファイルには、それぞれスパム
とスパムではないメールのサンプルが、行ごとに格納されています。そして、それぞれのファイル ...
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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.