how to save loop result in multiple csv r

Question

I read multiple csv files and get a list of 11 data frames. Now I want to use each data frame in the list to get a new table and save it to a csv file with the origin name separately.

I read csv file by

path <- "D:/DATA/01/processdata/singlecity"
fileNames = list.files(path, pattern="*.csv$")
filePath <- sapply(fileNames, function(x){ 
paste(path,x,sep='/')}) 
dfs <- lapply(filePath, function(x){
read.csv(x, header=T)})

then get a list of dataframe like :

EU CHINA USA

for (i in data){
   y <- data.table(i)
   y <- dplyr::filter(y, grepl('2002|2003|2004|2005|2006', V2))
   write.csv(y, "y.csv')
}

what I want to output is that:

EU_t1.csv
CHINA_t2.csv
USA_t3.csv

I don't know how to use write.csv to return different files based on origin data frame name.

Do you have only these dataframes in the environment? Or there are other dataframes as well that you don't want to write? — Ronak Shah
– Ronak Shah, Commented Nov 21, 2020 at 9:10
I have other dataframes in the environment. But these dataframes already in a list since I read multiple cvs files at same time as a list. Also, I can only have these dataframes if needed. — Feixiang Sun
– Feixiang Sun, Commented Nov 21, 2020 at 9:15
data is that list with all the dataframes? What does names(data) return? — Ronak Shah
– Ronak Shah, Commented Nov 21, 2020 at 9:19
I edit the way to read csv files in main question. For names(data) , return EU.csv CHINA.csv US.csv Japan.csv UK.csv — Feixiang Sun
– Feixiang Sun, Commented Nov 21, 2020 at 9:25

Ronak Shah · Accepted Answer · 2020-11-21 10:02:58Z

2

You can try the following :

path <- "D:/DATA/01/processdata/singlecity"
fileNames = list.files(path, pattern="*.csv$", full.names = TRUE)

lapply(seq_along(fileNames), function(x){
  file <- fileNames[x]
  data <- subset(read.csv(file), grepl('2002|2003|2004|2005|2006', V2))
  write.csv(data, sprintf('D:/DATA/01/processdata/singlecity/T1/%s_t%d.csv', 
            tools::file_path_sans_ext(basename(file)), x), row.names = FALSE)
})

edited Nov 21, 2020 at 10:02

answered Nov 21, 2020 at 8:34

Ronak Shah

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3 Comments

Feixiang Sun Over a year ago

How to deal with different data frame names, for example A, B ,C, how to export A_t.csv, B_t.csv, C_t.csv, also how to write into a new path

Feixiang Sun Over a year ago

Thank you, it works, great! Also, how to save these new files to a different path rather same path? For example:new_path <- "D:/DATA/01/processdata/singlecity/T1"

Ronak Shah Over a year ago

You can add the path in sprintf directly. See updated answer

Eric Leung · Accepted Answer · 2020-11-21 08:42:12Z

0

Here's a solution modifying the for loop you've shared.

dfs <- list(dataframe1, dataframe2, dataframe3)

for (i in seq_along(dfs)) {
   y <- data.table(dfs[[i]])
   y <- dplyr::filter(y, grepl('2002|2003|2004|2005|2006', V2))
   write.csv(y, paste0("datafram_t", i, ".csv"))
}

This will create files with the names you've requested:

datafram_t1.csv
datafram_t2.csv
datafram_t3.csv

answered Nov 21, 2020 at 8:42

Eric Leung

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