Pull elements from a list of lists in R using tidy principles-CodePudding

I have a list of lists and I wish to extract specific elements from each list and store the results in a data frame.

For each VendorNum I wish to extract n and MAD.conformity. In the example below there are 4 VendorNum.

The list of lists can be obtained by running the following chunk:

result <- top_vendors %>% 
  split(.$VendorNum) %>% 
  map(~ benford(number.of.digits = 1, discrete = TRUE, sign = "positive", data = .x$Amount))

Using map_dfr and extract I can pull a single element from each list but keep running into errors when I add additional elements.

Here's a reprex of what I am working with:

library(dplyr)
library(purrr)
library(benford.analysis)

data(corporate.payment)

# FIND VENDORS WITH A SIGNIFICANT NUMBER OF ROWS
vendor_records <- corporate.payment %>% 
  group_by(VendorNum) %>% 
  summarise(records = n()) %>% 
  arrange(desc(records))

# FILTER FOR THESE VENDORS
top_vendors <- corporate.payment %>% 
  filter(VendorNum %in% c('3630','6661','2001','4984'))

result <- top_vendors %>% 
  split(.$VendorNum) %>% 
  map(~ benford(number.of.digits = 1, discrete = TRUE, sign = "positive", data = .x$Amount)) %>% 
  map_dfr(magrittr::extract, c("MAD.conformity"), .id = "VendorNum")

When I add a vector of elements to the extract function I get the following error:

map_dfr(magrittr::extract, c("MAD.conformity","n"), .id = "VendorNum")

Error:
! Column names `MAD.conformity`, `MAD.conformity`, and `MAD.conformity` must not be duplicated.
Use .name_repair to specify repair.
Caused by error in `stop_vctrs()`:
! Names must be unique.
x These names are duplicated:
  * "MAD.conformity" at locations 1, 2, 3, and 4.
Run `rlang::last_error()` to see where the error occurred.
Warning message:
Outer names are only allowed for unnamed scalar atomic inputs

I'd be very grateful if you could help me figure out how to extract the extra elements into a data frame.

CodePudding user response：

to_extract <- list(MAD.conformity = c('MAD.conformity'),
                   n = c('info', 'n')) 
top_vendors %>% 
   split(.$VendorNum) %>% 
   map(~ benford(number.of.digits = 1, discrete = TRUE, sign = "positive", data = .x$Amount)) %>% 
   map_df(~map(to_extract, ~.y[[.x]], .x), .id = 'VendorNum')

# A tibble: 4 x 3
  VendorNum MAD.conformity            n
  <chr>     <chr>                 <int>
1 2001      Nonconformity          4735
2 3630      Acceptable conformity 13361
3 4984      Acceptable conformity  4311
4 6661      Nonconformity          4133