CODEWITHSUNDEEP
rapplylapply
chamaoskurumi
chamaoskurumi

Reputation: 2493

Manipulate same variable in a list of dataframes using lapply or Map

I managed to import 10 .csv files by making use this elegant lapply solution. The output now is a list of 10 data.frames. Each data.frame contains the variables year and value:

 file_names <- dir("../XYZ", pattern = glob2rx("*.csv"))
 data_list <- lapply(filenames, read.table, header = TRUE)
 head(data_list[[1]])
  year     value
1 200712   2320,00 
2 200712   120,00    
3 200712   188,00 
4 200712   1328,00    
5 200712   46,00    
6 200712   98,00 
 head(data_list[[2]])
  year     value
1 200812   320,00 
2 200812   1120,00    
3 200812   1288,00 
4 200812   1128,00    
5 200812   746,00    
6 200812   938,00

Unfortunately, the variable year is formatted yyyymm, but I want it to be yyyy.

Hence I would like to use another lapply or Map to change the format of year in every single data.frame. Something like:

data_list <- lapply(data_list[["year"]], FUN = substr(1,4), ... )

or:

data_list <- Map(substr(1,4), data_list, "year")

But that doesn't work...Any ideas?

Upvotes: 1

Views: 64

Answers (1)

akrun
akrun

Reputation: 887048

You could try 

data_list <- lapply(data_list, function(x) {x$year <- substr(x$year, 1,4)
                                   x})

Upvotes: 1

Related Questions