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.
12.1
カテゴリ型データ
397
Out[19]:
0 apple
1 orange
0 apple
0 apple
0 apple
1 orange
0 apple
0 apple
dtype: object
このような整数表現を、カテゴリ表現やディクショナリ形式にエンコードされた表現と呼びます。ま
た、もともとのユニークな値を並べた配列を、データのカテゴリやディクショナリ、レベルと呼びます。
この本ではカテゴリという用語を使っていきます。各カテゴリを参照している整数値は、カテゴリコー
ドもしくは単にコードと呼びます。
カテゴリ表現にすることで、分析を行う場合は処理速度をかなり改善できます。さらに、コードを変
更せずにカテゴリ情報だけを変更することも可能になります。比較的低コストで行えるカテゴリ情報の
変更としては、例えば次のようなものがあります。
●
カテゴリ名を変
更すること
●
既にあるカテゴリの順序や位置を変えずに、新たなカテゴリを追加すること
12.1.2
pandas
におけるカテゴリ型
pandas
には、データの保持に整数ベースのカテゴリ表現（エンコーディングとも言います）を用いる、
Categorical
という特殊な型があります。先ほどのシリーズの例を引き続き用いて考えていきましょう。
In [20]: fruits = ['apple', 'orange', 'apple', 'apple'] * 2
In [21]: N = len(fruits)
In [22]: df = pd.DataFrame({'fruit': ...
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.