Apply common header names to all files in the folder - r

Question

I have 4 files in the folder named import_xxx.xlsx.
I need to apply below tasks,
1.First apply common header names to all files in the folder.
Write the applied corrections as seperate file in another folder.
I have tried below code.
1.Read the list of files
filenames_list <- list.files(pattern= ".xls", full.names=TRUE)
My question is how to search for header names and apply naming the changed name to all files.
My column names is as follows with sample data.
Sr No Invoice Date Invoice No Payer Name IGMNo Container No Size Type Act. gate in Date Container Agent Container Agent Name Importer Name CHA Code CHA Name Activity Description Amount Service Tax Total
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 8-1-2018 12:12:29 AM MII180800001 SAME DEUTZ FAHR INDIA PRIVATE LIMITED 2200750 ECMU9674562 40 GB 7-26-2018 4:50:35 AM CLC007 CMA CGM SAME DEUTZ FAHR INDIA PRIVATE LIMITED CHS020 SEAKING CARGO SERVICES (I) PVT LTD Handling & PNR Movement Charges-FCL 10400 1872 12272
2 8-1-2018 12:12:29 AM MII180800001 SAME DEUTZ FAHR INDIA PRIVATE LIMITED 2200750 ECMU9674562 40 GB 7-26-2018 4:50:35 AM CLC007 CMA CGM SAME DEUTZ FAHR INDIA PRIVATE LIMITED CHS020 SEAKING CARGO SERVICES (I) PVT LTD Value Added Charges 2000 360 2360
I need to perform below data transformation tasks, which converts lower case characters to upper case characters. i.e column of activity desciption.
data.frame(lapply(df$Activity Description, function(v) {
if (is.character(v)) return(toupper(v))
else return(v)
}))
Do I need to loop through the files to write it? Following code will write the file but I need to loop through and write the applied changes for all files.
write.xlsx2(filename,"path")
Can anyone help me on this to loop through files and perform header transformation and write the files within the loop?
Thanks.

Answer 1

I would do something along the lines of the following. You will have to define the vector with the new common header, common_header.
(Untested.)
library(xlsx)
filenames_list <- list.files(pattern= "\\.xls", full.names=TRUE)
target_dir <- "path/to/target/directory/"
lapply(filenames_list, function(fl){
DF <- read.xlsx2(fl)
names(DF) <- common_header
target_fl <- paste0(target_dir, basename(fl))
write.xlsx2(DF, target_fl)
})