如何将 dplyr 组写入单独的文件? [英] How can I write dplyr groups to separate files?

问题描述

我正在尝试为使用 dplyr 的 group_by 函数分组的数据框中的每个组创建单独的 .csv 文件.到目前为止，我有类似的东西

I'm trying to create separate .csv files for each group in a data frame grouped with dplyr's group_by function. So far I have something like

by_cyl <- group_by(mtcars, cyl)
do(by_cyl, write_csv(., "test.csv"))

正如预期的那样，这会写入一个仅包含最后一组数据的 .csv 文件.如何修改它以写入多个 .csv 文件，每个文件的文件名都包含 cyl?

As expected, this writes a single .csv file with only the data from the last group. How can I modify this to write multiple .csv files, each with filenames that include cyl?

推荐答案

您可以将 csv 写入过程包装在自定义函数中，如下所示.请注意，该函数必须返回一个 data.frame 否则返回错误 Error: Results are not data frames at position

You can wrap the csv write process in a custom function as follows. Note that the function has to return a data.frame else it returns an error Error: Results are not data frames at positions

这将返回 3 个名为mtcars_cyl_4.csv"、mtcars_cyl_6.csv"和mtcars_cyl_8.csv"的 csv 文件

This will return 3 csv files named "mtcars_cyl_4.csv","mtcars_cyl_6.csv" and "mtcars_cyl_8.csv"

customFun  = function(DF) {
write.csv(DF,paste0("mtcars_cyl_",unique(DF$cyl),".csv"))
return(DF)
}

mtcars %>% 
group_by(cyl) %>% 
do(customFun(.))

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