对多个dplyr过滤条件使用整洁的评估 [英] Using tidy eval for multiple dplyr filter conditions
问题描述
我是不熟悉eval并尝试编写泛型函数的新手-我现在正努力解决的一件事是为分类变量编写多个过滤条件.这就是我现在正在使用的-
I'm new to tidy eval and trying to write generic functions- one thing I'm struggling with right now is writing multiple filter conditions for categorical variables. This is what I'm using right now-
create_expr <- function(name, val){
if(!is.null(val))
val <- paste0("c('", paste0(val, collapse = "','"), "')")
paste(name, "%in%", val)
}
my_filter <- function(df, cols, conds){
# Args:
# df: dataframe which is to be filtered
# cols: list of column names which are to be filtered
# conds: corresponding values for each column which need to be filtered
cols <- as.list(cols)
conds <- as.list(conds)
args <- mapply(create_expr, cols, conds, SIMPLIFY = F)
if(!length(args))
stop(cat("No filters provided"))
df <- df %>% filter_(paste(unlist(args), collapse = " & "))
return(df)
}
my_filter(gapminder, cols = list("continent", "country"),
conds = list("Europe", c("Albania", "France")))
我想知道如何使用整洁的评估实践将其重写.我已经找到了关于对多个参数使用quos()的资料,但是正如您所看到的,我在这里有两个不同的参数列表,这些列表需要相互映射.
I want to know how this could be re-written using tidy eval practices. I've found material on using quos() for multiple arguments but as you can see I have two different lists of arguments here which need to be mapped to each other.
感谢您的帮助,谢谢!
推荐答案
使用tidyverse,您可以将该函数重写为
Using the tidyverse, you could re-write that function as
library(dplyr)
library(purrr) # for map2()
my_filter <- function(df, cols, conds){
fp <- map2(cols, conds, function(x, y) quo((!!(as.name(x))) %in% !!y))
filter(df, !!!fp)
}
my_filter(gapminder::gapminder, cols = list("continent", "country"),
conds = list("Europe", c("Albania", "France")))
这相当于...
filter(gapminder, continent %in% "Europe", country %in% c("Albania", "France"))
起作用的主要原因是您可以将多个参数传递给filter()
,并且它们与&
隐式组合.而map2()
只是mapply
的最上等式,具有两个要迭代的对象.
The main reason this works is that you can pass multiple arguments to filter()
and they are implicitly combined with &
. And map2()
is just a tidyverse equivalent for mapply
with two objects to iterate.
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