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@swathci

VBAユーザがPython・Rを使ってみた：文字列操作（続）

Last updated at Posted at 2021-01-18

はじめに

機械学習の勉強を始めたVBAユーザです。
備忘録としてPython・Rの文法をVBAと比較しながらまとめていきたいと思います。

目次

文字列操作

以前の記事では、PythonとRの文字列操作についてVBAとの比較をしましたが、その続きで、Rの文字列操作のパッケージstringrを使ってみます。

参考記事に「R標準のbaseパッケージが提供する関数でも文字列処理は可能だが、 stringrのほうが統一的なインターフェイスに合理的な挙動で使いやすい。」とありますが、実際に使ってみると、確かに、関数のネーミングと引数の順序に統一性があって、感動的に使いやすいです。
参考：stringr — Rの文字列をまともな方法で処理する

文字列の結合

R(stringr)

R
library(stringr)

s1 <- "abc"
s2 <- "def"
s3 <- "ghij"
str_c(s1, s2, s3)
# "abcdefghij"

文字列の長さ

R(stringr)

R
s <- "abcdefghij"
str_length(s)
# 10

文字列の取り出し

R(stringr)

R
s <- "abcdefghij"
str_sub(s, 1, 2)
# "ab"
str_sub(s, -2, -1)
# "ij"
str_sub(s, 4, 6)
# "def"

文字列の検索

R(stringr)

R
s <- "abcdefghij"
t <- str_c(s, s, sep="") # "abcdefghijabcdefghij"
str_detect(s, "def")
# TRUE
str_detect(t, "def")
# TRUE
str_count(s, "def")
# 1
str_count(t, "def")
# 2
str_locate(s, "def")
#      start end
# [1,]     4   6
str_locate(t, "def")
#      start end
# [1,]     4   6
class(str_locate(t, "def"))
# "matrix"
str_locate_all(t, "def")
# [[1]]
#      start end
# [1,]     4   6
# [2,]    14  16
class(str_locate_all(t, "def"))
# "list"

文字列の置換

R(stringr)

R
s <- "abcdefghij"
t <- str_c(s, s, sep="") # "abcdefghijabcdefghij"
str_replace(s, "def", "DEF")
# "abcDEFghij"
str_replace(t, "def", "DEF")
# "abcDEFghijabcdefghij"
str_replace_all(t, "def", "DEF")
# "abcDEFghijabcDEFghij"

文字列の変換

大文字と小文字の変換

R(stringr)

R
s <- "abcDEFghij"
str_to_upper(s)    # 大文字に
# "ABCDEFGHIJ"
str_to_lower(s)    # 小文字に
# "abcdefghij"
str_to_title(s)    # 先頭のみ大文字・それ以外は小文字に
# "abcdefghij"
str_to_sentence(s) # 先頭のみ大文字・それ以外は小文字に
# "Abcdefghij"

ss <- "abc def ghij"
str_to_title(ss)
# "Abc Def Ghij"
str_to_sentence(ss)
# "Abc def ghij"

t <- ""
for (i in 1:str_length(s)) {
  stemp = str_sub(s,i,i)
  if (stemp == str_to_lower(stemp)) {
    stemp = str_to_upper(stemp)
  } else if (stemp == str_to_upper(stemp)) {
    stemp = str_to_lower(stemp)
  }
  t <- str_c(t, stemp)
}
t                     # 大文字・小文字の入れ替え
# "ABCdefGHIJ"
s == str_to_upper(s)  # すべて大文字かどうかの判定
# FALSE
s == str_to_lower(s)  # すべて小文字かどうかの判定
# FALSE

全角と半角の変換

R(stringr)

R

文字列の反転

R(stringr)

R
s <- "abcdefghij"
t <- ""
for (i in 1:str_length(s)) {
  t <- str_c(t, str_sub(s, -i, -i))
}
t
# "jihgfedcba"

文字列の繰り返し

R(stringr)

R
str_dup("A", 3)
# "AAA"
str_dup("def", 3)
# "defdefdef"

スペース

スペースの文字列

R(stringr)

R
str_c("-", str_dup(" ", 3), "-")
# "-   -"
# "-   -"
s <- str_c(str_dup(" ", 2), "d",
           str_dup(" ", 3), "e",
           str_dup(" ", 4), "f",
           str_dup(" ", 5))
str_c("-", s, "-")
# "-  d   e    f     -"

前後の不要なスペースの削除

R(stringr)

R
str_trim(s, side="left")
# "d   e    f     "
str_trim(s, side="right")
# "  d   e    f"
str_trim(s, side="both")
# "d   e    f"

文字列ベクトルについて

stringrパッケージの関数は、文字列（1個の文字列）だけでなく、文字列のベクトルやデータフレームでも使えます。
例えば、3個の文字列からなる文字列ベクトルにstr_length関数を使うと、その各要素の文字列に対してそれぞれstr_length関数を使った結果の数値3個からなるベクトルが返ります。

R(stringr)

R
s1 <- "abcdefghij"
s2 <- "cdefghijkl"
s3 <- "efghijklmn"
ss <- c(s1, s2, s3)
ss
# [1] "abcdefghij" "cdefghijkl" "efghijklmn"

str_c(ss, "_1")
# [1] "abcdefghij_1" "cdefghijkl_1" "efghijklmn_1" 

str_length(ss)
# [1] 10 10 10

str_sub(ss, 1, 2)
# [1] "ab" "cd" "ef"
str_sub(ss, -2, -1)
# [1] "ij" "kl" "mn"
str_sub(ss, 2, 3)
# [1] "bc" "de" "fg"

str_detect(ss, "def")
# [1]  TRUE  TRUE FALSE
str_count(ss, "def")
# [1] 1 1 0
str_locate(ss, "def")
#      start end
# [1,]     4   6
# [2,]     2   4
# [3,]    NA  NA
str_locate_all(ss, "def")
# [[1]]
#      start end
# [1,]     4   6
# 
# [[2]]
#      start end
# [1,]     2   4
# 
# [[3]]
#      start end
# 

str_replace(ss, "def", "DEF")
# [1] "abcDEFghij" "cDEFghijkl" "efghijklmn"
str_replace_all(ss, "def", "DEF")
# [1] "abcDEFghij" "cDEFghijkl" "efghijklmn"

str_to_upper(ss)
# [1] "ABCDEFGHIJ" "CDEFGHIJKL" "EFGHIJKLMN"
str_to_lower(ss)
# [1] "abcdefghij" "cdefghijkl" "efghijklmn"
str_to_title(ss)
# [1] "Abcdefghij" "Cdefghijkl" "Efghijklmn"
str_to_sentence(ss)
# [1] "Abcdefghij" "Cdefghijkl" "Efghijklmn"

ss == str_to_upper(ss)
# [1] FALSE FALSE FALSE
ss == str_to_lower(ss)
# [1] TRUE TRUE TRUE

str_dup(ss, 2)
# [1] "abcdefghijabcdefghij" "cdefghijklcdefghijkl" "efghijklmnefghijklmn"

tt <- str_c(" ", ss, " _1 ")
tt
# [1] " abcdefghij _1 " " cdefghijkl _1 " " efghijklmn _1 "
str_trim(tt)
# [1] "abcdefghij _1" "cdefghijkl _1" "efghijklmn _1"
str_trim(tt, side="left")
# [1] "abcdefghij _1 " "cdefghijkl _1 " "efghijklmn _1 "
str_trim(tt, side="right")
# [1] " abcdefghij _1" " cdefghijkl _1" " efghijklmn _1"

ベクトルやデータフレームについては、また別の記事でまとめたいと思います。

まとめ

一覧

各言語で使用する文字列操作関数等を一覧にまとめます。比較のために、EXCELでの計算も示しました。
s1 = "abc"
s2 = "def"
s3 = "ghij"
s = "abcdefghij"
t = "abcdefghijabcdefghij"
u = "abcDEFghij"
v = "ａｂｃＤＥＦｇｈｉｊ"
w = " d e f "
とします。また、EXCELのセルにそれぞれ
A1セル：="abc"
A2セル：="def"
A3セル：="ghij"
A4セル：="abcdefghij"
A5セル：="abcdefghijabcdefghij"
A6セル：="abcDEFghij"
A7セル：="ａｂｃＤＥＦｇｈｉｊ"
A8セル：=" d e f "
が入力されているものとします。

文字列の基本的操作

||Python|R|R(stringr)|VBA|EXCEL|結果|
|:--|:--|:--|:--|:--|:--|:--|:--|
|結合|s1 + s2 + s3|paste0(s1, s2, s3)
paste(s1, s2, s3, sep="")|str_c(s1, s2, s3)|s1 & s2 & s3|=A1&A2&A3
=CONCATENATE(
A1,A2,A3)|abcdefghij|
|長さ|len(s)|nchar(s)|str_length(s)|Len(s)|=LEN(A4)|10|
|反転|s[::-1]|||StrReverse(s)||jihgfedcba|
|繰り返し|'A' * 3||str_dup("A", 3)|String(3, "A")|=REPT("A",3)|AAA|
|繰り返し|'def' * 3||str_dup("def", 3)||=REPT("def",3)|defdefdef|

文字列の取り出し

||Python|R|R(stringr)|VBA|EXCEL|結果|
|:--|:--|:--|:--|:--|:--|:--|:--|
|左から|s[8:10]
s[0:2]
s[:2]|substr(s, 1, 2)
substring(s, 1, 2)|str_sub(s, 1, 2)|Left(s, 2)|=LEFT(A4,2)|ab|
|右から|s[len(s)-2:len(s)]
s[-2:]|substr(s,
nchar(s)-2+1,
nchar(s))|str_sub(s, -2, -1)|Right(s, 2)|=RIGHT(A4,2)|ij|
|途中|s[3:6]|substr(s, 4, 6)|str_sub(s, 4, 6)|Mid(s, 4, 3)|=MID(A4,4,3)|def|
注意）「途中」の文字列の取り出しについて、Python, Rの関数では取り出す文字列を「どこからどこまで」と指定しますが、VBA, EXCELの関数では「どこから何文字分」と指定します。

文字列の検索

||Python|R|R(stringr)|VBA|EXCEL|結果|
|:--|:--|:--|:--|:--|:--|:--|:--|
|検索|s.find('def')||str_locate(s, "def")|InStr(1, s, "def")|=FIND("def",A4,1)
=SEARCH("def",A4,1)|3,4|
|後ろからの検索|t.rfind('def')||||InStrRev(t, "def")|13,14|
|カウント|t.count('def')||str_count(t, "def")|||2|
注意）str_detect, str_locate関数については、上記参照。

文字列の置換

||Python|R|R(stringr)|VBA|EXCEL|結果|
|:--|:--|:--|:--|:--|:--|:--|:--|
|置換|s.replace('def', 'DEF')|sub("def", "DEF", s)|str_replace(s, "def", "DEF")|Replace(s, "def", "DEF")|=SUBSTITUTE(
A4,"def","DEF")
=REPLACE(A4,
FIND("def",A4),
LEN("def"),"DEF")|abcDEFghij|
|最初の1つだけ置換||sub("def", "DEF", t)|str_replace(t, "def", "DEF")|||abcDEFghij
abcdefghij|
|すべて置換|t.replace('def', 'DEF')|gsub("def", "DEF", t)|str_replace_all(t, "def", "DEF")|Replace(t, "def", "DEF")|=SUBSTITUTE(
A5,"def","DEF")|abcDEFghij
abcDEFghij|

文字列の変換

||Python|R|R(stringr)|VBA|EXCEL|結果|
|:--|:--|:--|:--|:--|:--|:--|:--|
|大文字に|u.upper()|toupper(u)|str_to_upper(u)|UCase(u)|=UPPER(A6)|ABCDEFGHIJ|
|小文字に|u.lower()|tolower(u)|str_to_lower(u)|LCase(u)|=LOWER(A6)|abcdefghij|
|先頭のみ大文字・それ以外は小文字に|u.capitalize()||str_to_title(u)
str_to_sentence(u)|StrConv(u, vbProperCase)|=PROPER(A6)|Abcdefghij|
|大文字と小文字を入れ替え|u.swapcase()|chartr("A-Za-z", "a-zA-z", u)||||ABCdefGHIJ|
|大文字かどうかの判定|u.isupper()|u == toupper(u)|u == str_to_upper(u)|||False|
|小文字かどうかの判定|u.islower()|u == tolower(u)|u == str_to_lower(u)|||False|
|全角に||chartr("A-Za-z", "Ａ-Ｚａ-ｚ", u)||StrConv(u, vbWide)|=JIS(A6)|ａｂｃＤＥＦｇｈｉｊ|
|半角に||chartr("Ａ-Ｚａ-ｚ", "A-Za-z", v)||StrConv(v, vbNarrow)|=ASC(A7)|abcDEFghij|

文字列のスペース

||Python|R|R(stringr)|VBA|EXCEL|結果|
|:--|:--|:--|:--|:--|:--|:--|:--|
|スペース|' ' * 3||str_dup(" ", 3)|Space(3)|=REPT(" ",3)|" "|
|両側スペース削除|w.strip(' ')||str_trim(s, side="both")|Trim(w)|=TRIM(A8)|"d e f"|
|左スペース削除|w.lstrip(' ')||str_trim(s, side="left")|LTrim(w)||"d e f "|
|右スペース削除|w.rstrip(' ')||str_trim(s, side="right")|RTrim(w)||" d e f"|
注意）EXCELのTRIM関数は文字列の中のスペースも1つを除いて削除されてd e fとなります。

プログラム全体

参考までに使ったプログラムの全体を示します。
Python, VBAのコードは前回の記事参照。

R(stringr)

R
library(stringr)

# 文字列の結合
s1 <- "abc"
s2 <- "def"
s3 <- "ghij"
str_c(s1, s2, s3)
# "abcdefghij"

# 文字列の長さ
s <- "abcdefghij"
str_length(s)
# 10

# 文字列の取り出し
s <- "abcdefghij"
str_sub(s, 1, 2)
# "ab"
str_sub(s, -2, -1)
# "ij"
str_sub(s, 4, 6)
# "def"

# 文字列の検索
s <- "abcdefghij"
t <- str_c(s, s, sep="") # "abcdefghijabcdefghij"
str_detect(s, "def")
# TRUE
str_detect(t, "def")
# TRUE
str_count(s, "def")
# 1
str_count(t, "def")
# 2
str_locate(s, "def")
#      start end
# [1,]     4   6
str_locate(t, "def")
#      start end
# [1,]     4   6
class(str_locate(t, "def"))
# "matrix"
str_locate_all(t, "def")
# [[1]]
#      start end
# [1,]     4   6
# [2,]    14  16
class(str_locate_all(t, "def"))
# "list"

# 文字列の置換
s <- "abcdefghij"
t <- str_c(s, s, sep="") # "abcdefghijabcdefghij"
str_replace(s, "def", "DEF")
# "abcDEFghij"
str_replace(t, "def", "DEF")
# "abcDEFghijabcdefghij"
str_replace_all(t, "def", "DEF")
# "abcDEFghijabcDEFghij"

# 文字列の大文字・小文字の変換
s <- "abcDEFghij"
str_to_upper(s)    # 大文字に
# "ABCDEFGHIJ"
str_to_lower(s)    # 小文字に
# "abcdefghij"
str_to_title(s)    # 先頭のみ大文字・それ以外は小文字に
# "abcdefghij"
str_to_sentence(s) # 先頭のみ大文字・それ以外は小文字に
# "Abcdefghij"

ss <- "abc def ghij"
str_to_title(ss)
# "Abc Def Ghij"
str_to_sentence(ss)
# "Abc def ghij"

t <- ""
for (i in 1:str_length(s)) {
  stemp = str_sub(s,i,i)
  if (stemp == str_to_lower(stemp)) {
    stemp = str_to_upper(stemp)
  } else if (stemp == str_to_upper(stemp)) {
    stemp = str_to_lower(stemp)
  }
  t <- str_c(t, stemp)
}
t                     # 大文字・小文字の入れ替え
# "ABCdefGHIJ"
s == str_to_upper(s)  # すべて大文字かどうかの判定
# FALSE
s == str_to_lower(s)  # すべて小文字かどうかの判定
# FALSE

# 文字列の反転
s <- "abcdefghij"
t <- ""
for (i in 1:str_length(s)) {
  t <- str_c(t, str_sub(s, -i, -i))
}
t
# "jihgfedcba"

# 文字列の繰り返し
str_dup("A", 3)
# "AAA"
str_dup("def", 3)
# "defdefdef"

# 文字列のスペース
str_c("-", str_dup(" ", 3), "-")
# "-   -"
# "-   -"
s <- str_c(str_dup(" ", 2), "d",
           str_dup(" ", 3), "e",
           str_dup(" ", 4), "f",
           str_dup(" ", 5))
str_c("-", s, "-")
# "-  d   e    f     -"

# 文字列の前後のスペース削除
str_trim(s, side="left")
# "d   e    f     "
str_trim(s, side="right")
# "  d   e    f"
str_trim(s, side="both")
# "d   e    f"


# 文字列ベクトル
s1 <- "abcdefghij"
s2 <- "cdefghijkl"
s3 <- "efghijklmn"
ss <- c(s1, s2, s3)
ss
# [1] "abcdefghij" "cdefghijkl" "efghijklmn"

str_c(ss, "_1")
# [1] "abcdefghij_1" "cdefghijkl_1" "efghijklmn_1" 

str_length(ss)
# [1] 10 10 10

str_sub(ss, 1, 2)
# [1] "ab" "cd" "ef"
str_sub(ss, -2, -1)
# [1] "ij" "kl" "mn"
str_sub(ss, 2, 3)
# [1] "bc" "de" "fg"

str_detect(ss, "def")
# [1]  TRUE  TRUE FALSE
str_count(ss, "def")
# [1] 1 1 0
str_locate(ss, "def")
#      start end
# [1,]     4   6
# [2,]     2   4
# [3,]    NA  NA
str_locate_all(ss, "def")
# [[1]]
#      start end
# [1,]     4   6
# 
# [[2]]
#      start end
# [1,]     2   4
# 
# [[3]]
#      start end
# 

str_replace(ss, "def", "DEF")
# [1] "abcDEFghij" "cDEFghijkl" "efghijklmn"
str_replace_all(ss, "def", "DEF")
# [1] "abcDEFghij" "cDEFghijkl" "efghijklmn"

str_to_upper(ss)
# [1] "ABCDEFGHIJ" "CDEFGHIJKL" "EFGHIJKLMN"
str_to_lower(ss)
# [1] "abcdefghij" "cdefghijkl" "efghijklmn"
str_to_title(ss)
# [1] "Abcdefghij" "Cdefghijkl" "Efghijklmn"
str_to_sentence(ss)
# [1] "Abcdefghij" "Cdefghijkl" "Efghijklmn"

ss == str_to_upper(ss)
# [1] FALSE FALSE FALSE
ss == str_to_lower(ss)
# [1] TRUE TRUE TRUE

str_dup(ss, 2)
# [1] "abcdefghijabcdefghij" "cdefghijklcdefghijkl" "efghijklmnefghijklmn"

tt <- str_c(" ", ss, " _1 ")
tt
# [1] " abcdefghij _1 " " cdefghijkl _1 " " efghijklmn _1 "
str_trim(tt)
# [1] "abcdefghij _1" "cdefghijkl _1" "efghijklmn _1"
str_trim(tt, side="left")
# [1] "abcdefghij _1 " "cdefghijkl _1 " "efghijklmn _1 "
str_trim(tt, side="right")
# [1] " abcdefghij _1" " cdefghijkl _1" " efghijklmn _1"

参考

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