[SOLVED] how to extract dataframe name from a list using map

how to extract dataframe name from a list using map

I tried to use 'map' to filter a list of dataset. how can I extract the name of dataframe, which is 'YYY' in my code.

library(dplyr)
library(purrr)

df1 <- data.frame(var1=seq(1:10), var2=seq(1:10), ID=1)
df2 <- data.frame(var2=seq(1:10), ID=2)
df3 <- data.frame(var3=seq(1:10), ID=3)
df_lst <- tibble::lst(df1, df2, df3)
codebook= data.frame(var.name = c("var1", "var2", "var3", "ID"),
                     df.name=c("df1", "df2", "df3", "ALL"))

try <- map(df_lst ~ {
data_sub <- codebook %>% filter(var.name %in% names(.x) & df.name %in% c( YYY, "ALL"))
.x %>% select(data_sub$var.name) 
})

Solution

purrr::imap() will pass the name of each element along with the element itself:

library(purrr)
library(dplyr)

imap(df_lst, \(df, nm) {
  data_sub <- codebook %>% 
    filter(var.name %in% names(df) & df.name %in% c(nm, "ALL"))
  df %>% select(data_sub$var.name) 
})

Note:

if you prefer formula-style lambdas (i.e., using ~ instead of \()), the names will be passed as .y.
the "manual" approach would be to iterate over names(df_list) instead of df_list, then access the dataframe within each iteration using df_list[[.x]].

Result: