filter verb to take list arguments

[IZ_r_user]

Hi RStudio community,

this is my first and I try my best to describe the problem I have so please be gentle

Aim: fill an empty tibble via a sequence of calls to dplyr::filter() where the arguments to this function call are provided from a list.

The list elements may be char or numeric and all of the same length.

Given what I have read in this post:

Passing named list to mutate (and probably other dplyr verbs)

Hi, I want to write a function that is given a named list which is then passed on to mutate() in a way that each element of the list is an argument to mutate(). I cannot get this right, either with the new quotation/quasi-quotation syntax or with the old mutate_() and would appreciate some help. Small example: foo <- function(x, args) { args <- enquote(args) mutate(x, UQS(args)) } foo(mtcars, args=list(cyl2=cyl*2)) foo <- function(x, args) { mutate_(x, .dots=args) } foo(mtcars, args=list(cyl2=cyl*2)) In both cases I get object 'cyl' not found when cyl exists in mtcars. I suppose the expression is not evaluated in the correct environment but I am not sure why. PS: I know that I cou…

what I came up with so far is this (and I do hope I did the repex right...):

library(tidyverse)

foo <- function(x, ...) {
args_quo <- rlang::quos(...)
filter(x, !!! args_quo)
}

my_cyl_values <- c(6, 8, 4)
my_carb_values <- c(4, 3, 1)

my_list_variables <- list(cyl = my_cyl_values, carb = my_carb_values)
len_filter <- length(my_list_variables[[1]])

data <- tibble(cyl = numeric(0), carb = numeric(0))

for (i in 1:len_filter) {
data_temp <- mtcars %>% foo(cyl == my_cyl_values[i], carb == my_carb_values[i])
data <- rbind(data, data_temp)
}

devtools::session_info()
#> ─ Session info ──────────────────────────────────────────────────────────
#> setting value
#> version R version 3.5.1 (2018-07-02)
#> os Linux Mint 19
#> system x86_64, linux-gnu
#> ui X11
#> language en_US
#> collate en_US.UTF-8
#> ctype en_US.UTF-8
#> tz Europe/Paris
#> date 2019-05-06

Now, the next step is to make this part nicer:
data_temp <- mtcars %>% foo(cyl == my_cyl_values[i], carb == my_carb_values[i])

Currently, a call to foo() provides the arguments manually i.e. the user has to specify cyl == ..., carb ==... herself.

This does not work for arbitrary lists of the same structure as "my_list_values" but with varying list elements/names.

What I mean by "the same structure as 'my_list_val'" is what I wrote in the beginning:

Arbitray list-length and names, but all elements of the list having the same size (so I can effectively loop over them, as above) and of type "char" or "numeric" (so the comparison with "==" makes sense).

I did look at the related post here

Using NSE to filter a list of lists by value

I do a lot of batch/parametric data analysis and have found that lists of lists that define/configure the processing tasks and hold the results next to the config that produced them are maximally flexible and convenient. This leads naturally to the condition where I want to filter my config/results using arbitrary boolean criteria applied to their values. I'm looking for or planning to implement something that operates in a manner similar to dplyr::filter or purrr::keep, but evaluates NSEs against the list elements and returns a subset of the original list containing the matches (i.e. rather than operating on rows in the context of tbls). Looking at quo(), UQ(), !!, etc. I think I see a pa…

but I did not understood the answer and felt there must be an easier way....