r - 条件赋值框架$col <- val with magrittr

Question

根据 Iris$Petal.Length 分配 Iris$column 的 Magrittr 语法是什么？没有 Magrittr 的示例:

df      <- iris[47:56,]
df$val1 <- NA                                           ## create column
df$val1[which(df$Petal.Length < 1.52)]                         <- "cake"
df$val1[which(df$Petal.Length > 1.55 & df$Petal.Length <=4.55)] <- "pie"
df$val1[which(df$Petal.Length > 4.55)]                        <- "apple"

head(df)

这会导致:

Petal.Length Petal.Width  Species    val1

1.6                0.2     setosa     pie

1.4                0.2     setosa     cake

1.5                0.2     setosa     cake

1.4                0.2     setosa     cake

1.4                1.4.  versicolor   apple

Answer 1

与您编写的内容完全等效的 magrittr 语法是:

df %>% transform(val1 = NA) %$%
  inset(.,Petal.Length < 1.52,"val1","cake") %$%
  inset(.,Petal.Length > 1.55 & Petal.Length <= 4.55,"val1","pie") %$%
  inset(.,Petal.Length > 4.55,"val1","apple")

或者对 magrittr 的别名非常热心:

df %>% transform(val1 = NA) %$%
  inset(.,Petal.Length %>% is_less_than(1.52),"val1","cake") %$%
  inset(.,Petal.Length %>% is_greater_than(1.55) & Petal.Length %>% 
  is_weakly_less_than(4.55),"val1","pie") %$%
  inset(.,Petal.Length %>% is_greater_than(4.55),"val1","apple")

还有一个变体:

df %>% transform(val1 = NA) %$%
  inset(.,Petal.Length %>% is_less_than(1.52),"val1","cake") %$%
  inset(.,Petal.Length %>% {is_greater_than(.,1.55) & is_weakly_less_than(.,4.55)},"val1","pie") %$%
  inset(.,Petal.Length %>% is_greater_than(4.55),"val1","apple")

前两个与基础中的严格等效(管道除外!):

df %>% transform(val1 = NA) %$%
  `[<-`(.,Petal.Length < 1.52,"val1","cake") %$%
  `[<-`(.,Petal.Length > 1.55 & Petal.Length <= 4.55,"val1","pie") %$%
  `[<-`(.,Petal.Length > 4.55,"val1","apple")

该变体相当于:

df %>% transform(val1 = NA) %$%
  `[<-`(.,Petal.Length < 1.52,"val1","cake") %$%
  `[<-`(.,Petal.Length %>% {`>`(.,1.55) & `<=`(.,4.55)},"val1","pie") %$%
  `[<-`(.,Petal.Length > 4.55,"val1","apple")

我使用 transform 因为它是一个 base 函数，而 mutate 是一个 dplyr 函数，但它们的工作原理相同就到这里。

有关所有别名的定义，请参阅:?extract