CODEWITHSUNDEEP
r
fifigoblin
fifigoblin

Reputation: 455

Get file name and assign it as a column name in a function

I've got several csv files that all have this format:

xyz         site
2.1         tex1
15.67       tex2
32.111      ny31

I want to import these files into R. Like this:

df_list <- list.files('./usa_data') 
dfs <- lapply(df_list, import_function)

What I want the import_function to do is to take a part of the name of the csv file and paste it instead of the first column name (xyz). My csv names have this format:

usa_low_dollars_270_1.csv
usa_high_euros_250_2.csv
usa_low_gbp_240_1.csv

I want to extract the currency (the third component of the name), combine it with the word 'median' and rename the first column like this:

dollars_median  site
2.1             tex1
15.67           tex2
32.111          ny31

# or 

euros_median  site
2.1             tex1
15.67           tex2
32.111          ny31

# etc

Upvotes: 1

Views: 465

Answers (2)

Ian Campbell
Ian Campbell

Reputation: 24770

You can use lapply along the indices of df_list using seq_along instead of on the vector itself.

From there you can subset df_list with the index and assign the column names of the read in data using strsplit.

df_list <- list.files()
df_list
[1] "usa_high_euros_250_2.csv"  "usa_low_dollars_270_1.csv" "usa_low_gbp_240_1.csv"   

lapply(seq_along(df_list), function(x){
  data <- read.csv(df_list[x])
  names(data)[1] <- str_c(strsplit(df_list[x],"_")[[1]][3],"_median")
  data
})
[[1]]
  euros_median site
1        2.100 tex1
2       15.670 tex2
3       32.111 ny31

[[2]]
  dollars_median site
1          2.100 tex1
2         15.670 tex2
3         32.111 ny31

[[3]]
  gbp_median site
1      2.100 tex1
2     15.670 tex2
3     32.111 ny31

Upvotes: 2

MarBlo
MarBlo

Reputation: 4524

You can extract the dollar or the other currencies on the 3. place of the string, so:

sp <- stringr::str_split("usa_low_dollars_270_1.csv", '_')[[1]][3]
sp
[1] "dollars"

you can then make your new name like so:

new <- paste0(sp, '_median')
new
[1] "dollars_median"

With this you can exchange the colname.

Upvotes: 1

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