"使用 R 將多個數據幀寫入 .csv 文件"

Question

我使用 lapply 將函數應用於多個數據幀：

data.cleaned <- lapply(data.list, shooter_cleaning)

Answer 1

這是理查德評論中的一個自包含示例，但使用列表中數據幀的名稱作為 CSV 文件的文件名：

# Create a list of n data frames

n <- 10

my_list <- lapply(1:n, function(i)  data.frame(x = rnorm(10), y = rnorm(10)) )

# name the data frames

names(my_list) <- letters[1:n]

# save each new data frame as an individual .csv file based on its name

lapply(1:length(my_list), function(i) write.csv(my_list[[i]], 
                                      file = paste0(names(my_list[i]), ".csv"),
                                      row.names = FALSE))

Answer 2

這是一種常見的操作。 您需要將數據幀拆分為數據幀list ，然后將它們寫入許多單獨的 csv。 我將演示 2 種使用基礎 R 的方法，以及 2 種使用 tidyverse 的方法。

基數R

for循環使迭代非常明確。

# example data.frame
df  <- data.frame(x = 1:4, y = c("a", "a", "b", "b"))

# split the dataframe into a list by the y column
l  <- split(df, df$y)

# make filepaths from list names, which are unique values of the y column
file_out <- paste0(names(l), ".csv")

# iterate over the list and the vector of list names to write csvs
for(i in 1:length(l)) {
  write_csv(l[[i]], file_out[i])
}

或者使用mapply() ：

mapply(
  function(x, y) write_csv(x, y), 
  l, 
  file_out
)

整理方法

library(tidyverse)

# we pass walk2 two inputs: a list of dataframes (.x) and filepaths (.y)
# `walk` is a silent `map` that doesn't print output to the console
walk2(l, file_out, ~write_csv(.x, .y))

或者，避免中間變量：

df %>% 
  group_split(y) %>% 
  walk(~write_csv(.x, paste0(.x$y[1], ".csv")))

Answer 3

如果這有幫助：我有一個包含多個數據框的環境，並且只有這些數據框，我想將每個數據框作為單獨的 CSV 文件輸出。 在 Ben 的回答的幫助下，並發現了mget ，我能夠使用以下代碼做到這一點：

for(i in 1:length(ls())) {
  write.table(
  mget(ls()[[i]]),
  file = paste0(ls()[[i]], ".csv"),
  sep = ";",
  qmethod = "double",
  row.names = FALSE)
}

Answer 4

這是使用purrr<\/code>在tibble<\/a>中寫入多個數據幀的表示：

# use functions from the 
# tidyr, stringr and purrr packages
library(tidyverse)
# create fake dataset
expand_grid(cat = c("a","b"),
            lev = "c",
            num = 1:2) %>% 
  # group and nest by `cat`
  group_by(cat) %>% 
  nest() %>% 
  ungroup() %>% 
  # create different file names with
  # the `cat` variable as reference
  # (you can also specify folder paths)
  mutate(file = map_chr(.x = cat,
                        .f = str_replace, 
                        "(.+)","\\1.csv")) %>% 
  # write each nested dataset 
  # in a separate file
  mutate(write = pmap(.l = select(.,x = data, file),
                      .f = write_csv))
#> # A tibble: 2 x 4
#>   cat   data             file  write           
#>   <chr> <list>           <chr> <list>          
#> 1 a     <tibble [2 x 2]> a.csv <tibble [2 x 2]>
#> 2 b     <tibble [2 x 2]> b.csv <tibble [2 x 2]>