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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176
11
章
stringr
による文字列
文字列全体とだけマッチするには、
^
と
$
の両方でアンカーします。
x <- c("apple pie", "apple", "apple cake")
str_view(x, "apple")
str_view(x, "^apple$")
単語境界のマッチに
\b
を使うことができます。私はR ではあまり使いませんが、RStudioで、他
の関数の部品になっている関数名を探すときに使います。例えば、
\bsum\b
を使って、
summarize
,
summary
,
rowsum
などとのマッチを避けます。
1. 文字列
"$^$"
とのマッチはどう行うか。
2. 頻出単語のコーパスが
stringr::words
にある。次のような単語をすべて探し出す正規表現を作
りなさい。
a.
"y"
で始まる。
b.
"x"
で終わる。
c. 正確に3 文字（
str_length()
を使ってズルをしないこと）。
d. 7 文字以上。
このリストは長いので、
str_view()
で
match
引数を使いマッチした、あるいは、マッチしな
かった単語だけを表示するとよい。
11.3.3
文字のクラスと候補
複数の文字にマッチする特別なパターンがいくつもあります。改行以外のどの文字ともマッチする
「
.
」は既に学びました。他に次の 4種類があります。
●
\d
はどの数字ともマッチする
●
\s
はどの空白文字（例、空白、タブ、改行）ともマッチする。
●
[abc]
は、
a
,
b
,
c
のどれかとマッチする。
●
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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.