R {dplyr} 0.5.0 新関数

case_when関数

dplyrをversionを新しくしたついでに何が追加されたかみていると
case_when関数というものが追加されてので使い方を確認しておく(URL)。

例えば

case_when(
  iris$Species == "setosa" ~ "1",
  iris$Species ==  "versicolor" ~ "2",
  iris$Species == "virginica" ~ "3" 
)

と書くと実行結果は以下の

 [1] "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1"
 [26] "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1"
 [51] "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2"
 [76] "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2" "2"
[101] "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3"
[126] "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3" "3"

ようになる。また、

case_when(
  iris$Sepal.Length < 5.5 ~ "1",
  iris$Sepal.Length < 6.5 ~ "2",
  iris$Sepal.Length >= 6.5~ "3" 
)

以下のように実行結果がなる。

  [1] "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "2" "2" "1" "1" "2" "1" "1" "1" "1"
 [24] "1" "1" "1" "1" "1" "1" "1" "1" "1" "1" "2" "1" "1" "2" "1" "1" "1" "1" "1" "1" "1" "1" "1"
 [47] "1" "1" "1" "1" "3" "2" "3" "2" "3" "2" "2" "1" "3" "1" "1" "2" "2" "2" "2" "3" "2" "2" "2"
 [70] "2" "2" "2" "2" "2" "2" "3" "3" "3" "2" "2" "2" "2" "2" "2" "1" "2" "3" "2" "2" "2" "2" "2"
 [93] "2" "1" "2" "2" "2" "2" "1" "2" "2" "2" "3" "2" "3" "3" "1" "3" "3" "3" "3" "2" "3" "2" "2"
[116] "2" "3" "3" "3" "2" "3" "2" "3" "2" "3" "3" "2" "2" "2" "3" "3" "3" "2" "2" "2" "3" "2" "2"
[139] "2" "3" "3" "3" "2" "3" "3" "3" "2" "3" "2" "2"

カテゴリー変数を作るには便利な関数だと思う。ただし、返り値がリストで帰ってきているのが注意点ぐらいだと思う。