Question

我可以在dplyr group_by中使用条件语句来基于另一个变量更改要分组的字段。这是一个starwars的简单示例：

library(dplyr)

my_val <- "Droid"
starwars %>%
  group_by(if(my_val == "Human") {eye_color}
            else if (my_val == "Droid") {homeworld}) %>%
  summarize(mass = sum(mass))

然而，resuls的列名称是条件语句的字符串：if (my_val == "Human") {\n eye_color\n} else if (my_val == "Droid") {\n homeworld\n}

我可以在条件之前输入一列名称：

group_by(Character_Type = if(my_val == "Human") {eye_color}
                          else if (my_val == "Droid") {homeworld}) %>%

但是我希望列名与条件语句中选择的列匹配，在此示例中为eye_color或homeworld。

如何将列名设置为与在条件语句中选择的字段相同？我可以将条件语句从dplyr语句中拉出，但是将其保留在内部会更简单。

Answer 1

喜欢吗？

library(dplyr)
 my_val <- "Droid"
 starwars %>%
   group_by(!!rlang::sym(ifelse(my_val == "Human","eye_color","homeworld"))) %>%
   summarize(mass = sum(mass))
# A tibble: 49 x 2
   homeworld       mass
   <chr>          <dbl>
 1 Alderaan          NA
 2 Aleen Minor       15
 3 Bespin            79
 4 Bestine IV       110
 5 Cato Neimoidia    90
 6 Cerea             82
 7 Champala          NA
 8 Chandrila         NA
 9 Concord Dawn      79
10 Corellia         157
# ... with 39 more rows

或

starwars %>%
  group_by(!!rlang::sym(case_when(my_val=="Droid"~"homeworld",
                                  my_val=="Human"~"eye_color"))) %>%
  summarize(mass = sum(mass))

Answer 2

我们可以使用group_by_at，它可以将字符串作为输入

library(dplyr)
starwars %>% 
  group_by_at(if_else(my_val == "Human", "eye_color", "homeworld")) %>% 
  summarise(mass = sum(mass))
# A tibble: 49 x 2
#   homeworld       mass
#   <chr>          <dbl>
# 1 Alderaan          NA
# 2 Aleen Minor       15
# 3 Bespin            79
# 4 Bestine IV       110
# 5 Cato Neimoidia    90
# 6 Cerea             82
# 7 Champala          NA
# 8 Chandrila         NA
# 9 Concord Dawn      79
#10 Corellia         157
# ... with 39 more rows

在条件dplyr group_by中更正列标签

2 个答案: