July 2018
Intermediate to advanced
596 pages
13h 35m
Japanese
Content preview from Pythonによるデータ分析入門 第2版 ―NumPy、pandasを使ったデータ処理
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.
12.2
グループ演算の使い方：応用編
405
メソッド 説明
remove_unused_categories
データに含まれていないカテゴリを削除する。
rename_categories
カテゴリ名のセットを、指定された新たなセットに入れ替える。その際にカテゴ
リの数を変えることはできない。
reorder_categories
動作は
rename_categories
と似ているが、戻すカテゴリの間に大小関係を設定
することもできる。
set_categories
カテゴリ名のセットを、指定された新たなセットに入れ替える。その際にカテゴ
リの追加や削除を行ってもよい。
12.1.4.1
モデリング用のダミー変数の作成
統計や機械学習用のツールを使用する際には、カテゴリ型データをダミー変数の形式（one-hotエン
コーディングとも言います）に変換しなければならないことがよくあります。具体的には、個々のカテ
ゴリがそれぞれ
1
つの列となっているデータフレームを作成し、それら
の列それぞれに、値がその列の
カテゴリとなっている要素では
1
、なっていない要素では
0
を設定する、という変換です。
先ほどの例でもう一度考えてみましょう。
In [73]: cat_s = pd.Series(['a', 'b', 'c', 'd'] * 2, dtype='category')
前に「7章 データのクリーニングと前処理」で説明したように、このような
1
次元のカテゴリ型デー
タは、
pandas.get_dummies
という関数を用いて
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.