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.
10.2
データの集約
325
10.2
データの集約
集約とは、何らかのデータ変形を行って配列からスカラー値を生成することを指します。先ほどの
例では、平均、個数のカウント、最小値、最大値などの集約を使いました。
GroupBy
オブジェクトに
対して
mean()
を呼び出すことで何が起こっているのか、もしかしたら不思議に思ったかもしれません。
表10-1に見られるような多くの一般的な集約については、既に最適化された実装が存在します。しか
し、これらのメソッドに限定されているわけではありません。
表10-1 最適化済みのGroupByメソッド
関数名 説明
count
グループ内の欠損値以外の値の数。
sum
欠損値以外の合計。
mean
欠損値以外の平均。
median
欠損値以外の算術中央値。
std
,
var
バイアスの掛かっていない（
n
−
1
を分母とした）標準偏差と分散。
min
,
max
欠損値以外の最小値と最大値。
prod
欠損値以外の積。
first
,
last
欠損値以外の最初と最後の値。
自分自身で考えた集約処理を使うこともできますし、グループ化されたオブジェクトに定義されてい
るメソッドを追加で呼ぶこともできます。例えば、グループ化されたオブジェクトに対して
quantile
メ
ソッドを呼ぶことができます。
quantile
メソッドは、シリーズやデータフレームの列の分位点を計算し
ます。
quantile
メソッドは
GroupBy
オブジェクトで実装されたものではありませんが、シリーズのメソッ
ドであるため、ここで使うことがで
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.