Question

基于Iris $ Petal.Length分配Iris $列的Magrittr语法是什么？没有Magrittr的例子：

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

我们可以使用case_when

res <- df %>% 
          mutate(val1 = case_when(Petal.Length < 1.52 ~ 'cake',
                  Petal.Length > 1.55 & Petal.Length <= 4.55 ~ 'pie',
                   Petal.Length > 4.55 ~'apple'))
head(res, 5)
#  Sepal.Length Sepal.Width Petal.Length Petal.Width    Species  val1
#1          5.1         3.8          1.6         0.2     setosa   pie
#2          4.6         3.2          1.4         0.2     setosa  cake
#3          5.3         3.7          1.5         0.2     setosa  cake
#4          5.0         3.3          1.4         0.2     setosa  cake
#5          7.0         3.2          4.7         1.4 versicolor apple

Answer 2

与您所写的完全相同的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")

一个变种：

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")

两个第一个在基础上严格等同于此（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")

变体等同于：

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

我使用了transform，因为它是base函数，而mutate是dplyr函数，但它们的工作方式相同。

有关所有别名的定义，请参阅：?extract

条件赋值框架$ col＆lt; - val with magrittr

2 个答案: