问题描述
我在根据变量选择负列时遇到问题。
我发现这里报告了一个类似的问题:
https://github.com/tidyverse/dplyr/issues/4813 但提供的解决方案不起作用(请参阅下面的 repex
)。
如果有人知道解决方法,那将不胜感激!!
这是问题的repex
:
# Load package
library(dplyr,warn.conflicts = F)
ex_data <- tibble(a = 1,b = 2)
# example functions
## Function for checking if target was provided
## else defaults to all numeric columns
check_target <- function(target) {
target
target_quoted <- rlang::enquo(target)
if (rlang::quo_is_null(target_quoted)) {
rlang::expr(where(is.numeric))
} else{
rlang::expr(!!target)
}
}
## Just soft wrappers to show how the preivews
## function Could be used
my_select_embrace <- function(data,target = NULL){
target <- check_target(target)
data %>%
select({{ target }})
}
my_select_bang <- function(data,target = NULL){
target <- check_target(target)
data %>%
select(!!target)
}
# Works
ex_data %>%
select(-1) %>%
invisible()
ex_data %>%
my_select_bang(tidyselect::vars_select_helpers$where(is.numeric)) %>%
invisible()
ex_data %>%
my_select_bang() %>%
invisible()
# Fails
ex_data %>%
my_select_embrace() %>%
invisible()
#> Error: object 'is.numeric' not found
ex_data %>%
my_select_bang(tidyselect::vars_select_helpers$contains('a')) %>%
invisible()
#> Error: `contains()` must be used within a *selecting* function.
#> i See <https://tidyselect.r-lib.org/reference/faq-selection-context.html>.
ex_data %>%
my_select_embrace(tidyselect::vars_select_helpers$where(is.numeric)) %>%
invisible()
minus_one <- -1
ex_data %>%
my_select_embrace(minus_one)
#> Error: Selections can't have negative values.
ex_data %>%
my_select_bang(minus_one)
#> Error: Selections can't have negative values.
由 reprex package (v2.0.0) 于 2021 年 6 月 21 日创建
解决方法
这是您要找的吗?
library(dplyr,warn.conflicts = F)
ex_data <- tibble(a = 1,b = 2)
my_select_bang <- function(data,target = NULL){
target_quoted <- enquo(target)
target_null <- rlang::quo_is_null(target_quoted)
data %>%
select(if (target_null) where(is.numeric) else !!target_quoted)
}
# defaults to `where(is.numeric)`
ex_data %>%
my_select_bang()
#> # A tibble: 1 x 2
#> a b
#> <dbl> <dbl>
#> 1 1 2
# works with tidyselect syntax as expected
ex_data %>%
my_select_bang(contains("a"))
#> # A tibble: 1 x 1
#> a
#> <dbl>
#> 1 1
由 reprex package (v0.3.0) 于 2021 年 6 月 21 日创建
如果您不介意在函数形式中使用默认值,那么下面的方法也适用:
my_select_bang <- function(data,target = tidyselect::vars_select_helpers$where(is.numeric)){
data %>%
select(!!target)
}
如果您想在向量中捕获 -1
并在 dplyr::select
或您自己的函数之一中使用它,您应该使用 minus_one <- expr(-1)
捕获它。那么它就不会抛出错误。
minus_one <- expr(-1)
ex_data %>%
my_select_bang(minus_one)
#> # A tibble: 1 x 1
#> b
#> <dbl>
#> 1 2
由 reprex package (v0.3.0) 于 2021 年 6 月 21 日创建
,使原始设计生效的一种方法是在将其发送到 target
之前引用 check_target
并使用 bang-bang
(!!
) 而不是拥抱 {{ arg }}
:
# Load package
library(dplyr,b = 2)
# example functions
## Function for checking if target was provided
## else defaults to all numeric columns
check_target <- function(target) {
if (rlang::quo_is_null(target)) {
rlang::expr(where(is.numeric))
} else{
target
}
}
## Just soft wrapper to show how the preivews
## function could be used
my_select_bang <- function(data,target = NULL){
target <- rlang::enquo(target)
target <- check_target(target)
data %>%
select(!!target)
}
# Works
ex_data %>%
select(-1) %>%
invisible()
ex_data %>%
select(contains('a')) %>%
invisible()
ex_data %>%
my_select_bang(where(is.numeric)) %>%
invisible()
ex_data %>%
my_select_bang() %>%
invisible()
ex_data %>%
my_select_bang(contains('a')) %>%
invisible()
ex_data %>%
my_select_bang(-1) %>%
invisible()
由 reprex package (v2.0.0) 于 2021 年 6 月 21 日创建