使用 purrr::walk 从带有动态文件名的嵌套数据帧写入

Question

我使用 purrr::map 将函数应用于嵌套数据框以获取新的数据框列表列。

现在我想使用同一行中的列值作为文件名的一部分将每个新数据帧写入文件。

我陷入了如何提取其他列值以便传递到文件名以写入文件的问题。我相信应该参与其中，但如何访问列变量和purrr::walk列表数据框内容的方式是问题所在。

代表如下：

library(tibble) 
library(dplyr)
library(tidyr)  
library(purrr)

# Data
data("mtcars")
mtcars_nest <- mtcars %>% rownames_to_column() %>% rename(rowname_1 = rowname) %>% select(-mpg) %>% group_by(cyl) %>% nest()
mtcars_mpg <- mtcars %>% rownames_to_column() %>% rename(rowname_2 = rowname) %>% select(rowname_2, mpg)

# Function to apply to nested dataframe
join_df <- function(df_nest, df_other) {
  df_all <- inner_join(df_nest, df_other, by = c("rowname_1" = "rowname_2"))
  return(df_all)
}

# 1. Apply function to `$data` to get new dataframe list column and add an extra 'case' column for filename
mtcars_nest %>%
  mutate(case = c("first", "second", "third")) %>%
  mutate(new_mpg = map(data, ~ join_df(., mtcars_mpg)))

# 2. Now write `$new_mpg` to file with filename sources from $cyl and $case
# I think `walk` is the correct to use but how to pass the two row values into filename?

## Not real code##
# mtcars_nest %>%
#  walk(., function(x) {write.csv(., file = paste0(cyl, "_", case, ".csv")})

Answer 1

使用pwalk：

... %>%
select(cyl, case, new_mpg) %>%
pwalk(~ write.csv(..3, file = paste0(..1, '_', ..2, '.csv')))

在您的代码之后链接：

mtcars_nest %>%
    mutate(case = c("first", "second", "third")) %>%
    mutate(new_mpg = map(data, ~ join_df(., mtcars_mpg))) %>%
    select(cyl, case, new_mpg) %>%
    pwalk(~ write.csv(..3, file = paste0(..1, '_', ..2, '.csv')))