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
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.
174
11
章
stringr
による文字列
複雑にしていきます。パターンマッチを習得したら、これらのアイデアをさまざまな
stringr
の関数
にどう使うかを学びます。
11.3.1
基本マッチ
最も単純なパターンマッチは厳密なマッチです。
x <- c("apple", "banana", "pear")
str_view(x, "an")
次のステップは、（改行以外の）どんな文字ともマッチする「
.
」です。
str_view(x, ".a.")
さて、「
.
」がどんな文字ともマッチするなら、文字「
.
」とのマッチはどうすればよいでしょうか。
特殊な振る舞いを行うのではなく、エスケープ文字を使って、正規表現に対して厳格な一致を行う
よう伝える必要があります。文字列同様、正規表現でもバックスラッシュ「\」を使って特別な振る舞
いからエスケープします。「
.
」とマッチするには「
\.
」とします。困ったことにこれでも問題が生じま
す。正規表現には文字列を使いますが、文字列でのエスケープには
\\
が使われます。従って、正規
表現の
\.
を作るには、文字列「
\\.
」が必要です。
#
正規表現を作るには
\\
が必要
dot <- "\\."
#
しかし、正規表現自体には
1
つしか含まれない
:
writeLines(dot)
#> \.
#
明示的な
.
を探すよう
R
に伝える
str_view(c("abc", "a.c", "bef"), "a\\.c")
正規表現で
\
がエスケープ文字に使われているなら、文字通りの
\
とマッチするにはどうすれば良
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.