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r - Tidyeval 评估 case_when

转载 作者:行者123 更新时间:2023-12-04 12:38:49 27 4
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Tidy evaluation programming with dplyr::case_when有些相关和 Making tidyeval function inside case_when ,我想创建字符串(使用 Shiny 的应用程序)稍后在 case_when 函数中进行解析。这是一个例子:

library(tidyverse)

# simulated shiny inputs
new_column = sym("COL_NAME")

number_of_categories = 3

col1_text = "Big"
col1_min = 7.0
col1_max = 8.0

col2_text = "Medium"
col2_min = 5.0
col2_max = 6.9

col3_text = "Small"
col3_max = 4.9
col3_min = 4.0

columninput = sym("Sepal.Length")

期望的输出

iris %>%
mutate(new_column =
case_when(
!!columninput >= col1_min & !!columninput <= col1_max ~ col1_text,
!!columninput >= col2_min & !!columninput <= col2_max ~ col2_text,
!!columninput >= col3_min & !!columninput <= col3_max ~ col3_text
)
)

因为函数之间唯一改变的是索引,我想我们可以使用通用模式来创建一个字符串

# create single string
my_string <-function(i) {
paste0("!!", columninput, " >= col", i, "_min & ", "!!", columninput, " <= col", i, "_max ~ col", i, "_text")
}

然后为动态案例数重复字符串

mega_string <- map_chr(1:number_of_categories, ~ my_string(.x))

待办事项:

这是我无法完全拼凑的部分:使用这些字符串作为 case_when 中的参数。

# evaluate somehow?
iris %>%
mutate(
new_column = case_when(
# tidyeval mega_string?
paste(mega_string, collapse = "," )
)
)

这是正确的方法吗?您还会如何解决这个问题 - 非常感谢任何高级别或其他方面的帮助!

最佳答案

我们可以创建一个表达式并求值

library(dplyr)
library(stringr)
iris %>%
mutate(new_column = eval(rlang::parse_expr(str_c('case_when(',
str_c(mega_string, collapse=","), ')'))))
# Sepal.Length Sepal.Width Petal.Length Petal.Width Species new_column
#1 5.1 3.5 1.4 0.2 setosa Medium
#2 4.9 3.0 1.4 0.2 setosa Small
#3 4.7 3.2 1.3 0.2 setosa Small
#4 4.6 3.1 1.5 0.2 setosa Small
#5 5.0 3.6 1.4 0.2 setosa Medium
#6 5.4 3.9 1.7 0.4 setosa Medium
#7 4.6 3.4 1.4 0.3 setosa Small
#8 5.0 3.4 1.5 0.2 setosa Medium
#9 4.4 2.9 1.4 0.2 setosa Small
#10 4.9 3.1 1.5 0.1 setosa Small
# ...

或者使用 parse_expr!!!

library(purrr)
iris %>%
mutate(new_column = case_when(!!! map(mega_string, rlang::parse_expr)))
# Sepal.Length Sepal.Width Petal.Length Petal.Width Species new_column
#1 5.1 3.5 1.4 0.2 setosa Medium
#2 4.9 3.0 1.4 0.2 setosa Small
#3 4.7 3.2 1.3 0.2 setosa Small
#4 4.6 3.1 1.5 0.2 setosa Small
#5 5.0 3.6 1.4 0.2 setosa Medium
#6 5.4 3.9 1.7 0.4 setosa Medium
#7 4.6 3.4 1.4 0.3 setosa Small
#8 5.0 3.4 1.5 0.2 setosa Medium
#...

关于r - Tidyeval 评估 case_when,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/61601797/

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