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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13.4
タイムスパン
219
duration
を足したり掛けたりできます。
2 * dyears(1)
#> [1] "63072000s (~2 years)"
dyears(1) + dweeks(12) + dhours(15)
#> [1] "38847600s (~1.23 years)"
duration
を日に足したり引いたりできます。
tomorrow <- today() + ddays(1)
last_year <- today() - dyears(1)
しかし、
duration
が正確な秒数を表すために、予期せぬ結果が得られることもあります。
one_pm <- ymd_hms(
"2016-03-12 13:00:00",
tz = "America/New_York"
)
one_pm
#> [1] "2016-03-12 13:00:00 EST"
one_pm + ddays(1)
#> [
1] "2016-03-13 14:00:00 EDT"
なぜ、3月12日午後1 時の1日後が3月13日の午後2 時となるのでしょう。この日付を注意して読
めば、タイムゾーン表示が異なっていることに気付きます。夏時間の開始により、3月12日には23
時間しかありませんでした。1日分の秒数を足したので、時刻が違ったのです。
13.4.2
period
（時期）
この問題を回避するため、
lubridate
は
period
を用意しました。
period
もタイムスパンですが、
秒数固定長ではありません。日や月といった ...
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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.