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.
11.2
時系列の基本
351
In [36]: idx
Out[36]: DatetimeIndex(['2011-07-06 12:00:00', '2011-08-06 00:00:00', 'NaT'], dty
pe='datetime64[ns]', freq=None)
In [37]: idx[2]
Out[37]: NaT
In [38]: pd.isnull(idx)
Out[38]: array([False, False, True], dtype=bool)
NaT
（
Not a Time
）というのは、
pandas
でのタイムスタンプ型のデータにおける欠損値のことです。
dateutil.parser
は便利ですが、完璧なツールではありません。というのも、一部の日付と
して認識して欲しくない文字列を日付と認識してしまいます。例えば、
'42'
は
2042
年の今
日の日付と認識されてしまいます。
datetime
オブジェクトは、他国や多言語における特定のロケール向けの書式オプションも多く持っ
ています（表11-3参照）。例えば、月の名前の省略形はドイツ語とフランス語では、英語と異なります。
表11-3 特定のロケール向けの日付書式
型 説明
%a
曜日の省略形。
%A
曜日を完全に表現したもの。
%b
月の省略形。
%B
月を完全に表現したもの。
%c
日付と時間を完全に表現したもの。例：「
Tue 01 May 2012 04:20:57 PM
」
%p
ロケールでの午前と午後を表したもの。
AM
や
PM
。
%x
ロケール
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.