library(readr)
library(tidyr)

file_path <- "C:/Users/user/Desktop/to_melt.csv"
input <- read_csv(file_path)

# create vector of field names that you want melted
## in this instance select the 8th field through end of data frame
fields_to_melt <- names(input[8:length(names(input))])

# melt the data from wide- to long-format
melted <- gather(input fields_to_melt key = variable value = values)

write_csv(melted C:/Users/user/Desktop/melted.csv)