November 2017
Intermediate to advanced
328 pages
6h 51m
Japanese
Content preview from 入門 PySpark ―PythonとJupyterで活用するSpark 2エコシステム
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94
6
章
ML
パッケージ
6.1.1
Transformer
Transformer
クラスは、その名のとおりデータを変換します。これは（通常は）新しい列を
DataFrameに追加することによって行われます。
高いレベルで見れば、抽象クラスの
Transformer
か ら ク ラ ス を 導 出 す る 場 合、 必
ず
.transform(...)
メソッドを実装しなければなりません。このメソッドには最初のパラメータと
して変換するDataFrameを渡さなければなりません。通常はこれが唯一必須のパラメータです。こ
れはもちろん、MLパッケージのメソッドごとに異なります。広く使われている他のパラメータとし
ては、
inputCol
と
outputCol
があります。ただしこれらは多くの場合、たとえば
inputCol
での
'features'
のようにデフォルトの値が事前に定義されています。
spark.ml.feature
には多くの
Transformer
が定義されています。次にそれらの概要を示しま
す（この中には本章で後ほど使っていくものもあります）。
●
Binarizer
：このメソッドは閾値を取り、与えられた連続的な変数を 2 値に変換します。
●
Bucketizer
：これは
Binarizer
に似ていますが、閾値のリスト（
splits
パラメータ）を受
け取り、連続変数を多値変数に変換します。
●
ChiSqSelector
：ターゲット変数がカテゴリ型の場合（クラシフィケーションモデルのこと
を考えてみて
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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.