October 2017
Intermediate to advanced
480 pages
9h 49m
Japanese
Content preview from Rではじめるデータサイエンス
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152
10
章
dplyr
による関係データ
要はありません。問題となる表の間の関係の繋がりを理解しさえすれば十分です。
nycflights13
は次の性質を持ちます。
●
flights
は変数
tailnum
で
planes
と結びつく。
●
flights
は変数
carrier
で
airlines
と結びつく。
●
flights
は変数
origin
と
dest
という2 通りで
airports
と結びつく。
●
flights
は
origin
（場所）および
year
,
month
,
day
,
hour
（時刻）で
weather
と結びつく。
1. 飛行機が出発地から目的地まで飛ぶルート（の概略）を描きたいとする。どの変数が必要か。ど
のような表を組み合わせるか。
2.
weather
と
airports
の関係を書き忘れた。関係はどのようなものか。図ではどのように表すか。
3.
weather
は出発空港（NYC）の天候しか含まない。もし、米国の全空港の天候記録を含むとすれ
ば、
flights
でどのような関係が追加されるか。
4. 一年の内には搭乗者数が他の日より少ない「特別な」日がある。そのデータをデータフレームで
どのように表すか。その表の主キーは何か。それは、現在の表とどのように結びつくか。
10.3
キー
表のペアを結びつける変数はキーと呼ばれます。キーは変数（または変数集合）で、観測を一意
に示します。単純なデータでは、1変数で観測を一意に示すことができます。例えば、飛行機は
tailnum
で一意に識別されます。複数の変数が必 ...
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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.