How to export multiple data frames to CSV?

Question

Situation: I have several data frames that I like to export as CSV files into the working directory for further processing.

Goal: Export a collection of data frames from the workspace as csv files to the working directory by using a single function (batch export).

Details:

My question is not about changing the content of the data frames, so you can just use any example data provided by R for reproduction.

The function I use for exporting a single data frame is

csvExport <- function(data, enc = 'utf8'){
    name <- paste(deparse(substitute(data)), "csv", sep=".")
    con <- file(name, encoding = enc)
    write.csv(data, file = con, row.names=FALSE, quote = TRUE, sep = ";")
    text<-"exported!"
    print(paste(name, text, sep=" "))
}

Since I do not like to call the function for each data frame to export explicitly I am looking for a way to export the data frames by indicating which ones from the workspace I like to export with:

export <- ls()[1:20]

I then tried using this function (with some variation of the for loop) with the above list:

multipleCSVExport <- function(export){
  for (i in export){
    csvExport(i)
  }
}

However, I am not able to create the expected result.

You'll probably need to re-write your csvExport function so that the data argument is a character, which is really what you should have done in the first place, most likely. get will be useful. — joran
– joran, Commented Jan 15, 2014 at 16:18
@ joran: This solved my problem, thanks. Maybe you can turn it into an answer. — fr3d-5
– fr3d-5, Commented Jan 15, 2014 at 17:06

dickoa · Accepted Answer · 2014-01-15 16:25:07Z

5

You can use mget to turn your data.frames in the workspace into a list of data.frame and then use lapply or a for loop.

list_df <- mget(ls()[1:20])

lapply(seq_along(list_df),
       function(i) write.table(list_df[[i]], 
                               paste0(names(list_df)[i], ".csv"),
                               row.names = FALSE, quote = TRUE, 
                               sep = ";", dec = "."))

answered Jan 15, 2014 at 16:25

dickoa

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Comments

Tyler Rinker · Accepted Answer · 2014-01-15 19:30:59Z

1

The qdap package has just such a function: mscv_w. The dev version is what you're after and can be downloaded here (follow directions): https://github.com/trinker/qdap#installation

So something like this works:

mcsv_w(mtcars, CO2, dir="foo")

And if you're more interested in how the function works here is the source code: https://github.com/trinker/qdap/blob/master/R/mcsv_r.R

answered Jan 15, 2014 at 19:30

Tyler Rinker

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