Reading .csv files, converting them and saving them as .xlsx using R - r

Question

I have a folder full of .csv files that have to be slightly changed and then saved as an xlsx document.
Herefore, I have created a Loop to do this:
library(xlsx)
docs <- Sys.glob( "*.csv" )
for( i in docs )
{
df <- read.csv(i)
df2 <- select(df, X, Y)
df3 <- mutate(df3, Z = (X - Y) / 3600)
write.xlsx(df3, paste( "C:/users/Desktop/Files/", i), row.names = FALSE)
}
However, when I execute this for loop, the following error message pops up:
Error in createWorkbook(type = ext) : Unknown format csv
Did I forget anything? I would be very grateful, if you could help me, as I have no idea what else to change...

Answer 1

The package rio removes most of the headache with xlsx files. It can also be used to read in files:
docs <- Sys.glob("*.csv")
for(i in docs) {
df <- rio::import(i)
df2 <- select(df, X, Y)
df3 <- mutate(df3, Z = (X - Y) / 3600)
rio::export(df3, paste0("C:/users/Desktop/Files/", i, ".xlsx"))
}
This should work on the import/export part. What I'm not so sure about is your Sys.glob, since I've never used that before. I find list.files has a really easy and powerful syntax...
Update
If you want to get rid of the .csv file extension, you can use this instead:
for(i in docs) {
df <- rio::import(i)
df2 <- select(df, X, Y)
df3 <- mutate(df3, Z = (X - Y) / 3600)
fname <- gsub(".csv$", "", i)
rio::export(df3, paste0("C:/users/Desktop/Files/", fname, ".xlsx"))
}