在tidyr :: gather中使用多个键

Question

I used to use reshape2::melt to perform the following, since I want to learn tidyr , I wonder how this can be done in tidyr::gather :

iris %>%
  as_tibble %>%
  mutate(country=rep(LETTERS[1:3],ceiling(n()/3))[1:n()]) %>%
  reshape2::melt(.,id.var=c('country','Species'))

Thanks!

Answer 1

Try

iris %>%
  as_tibble %>%
  mutate(country=rep(LETTERS[1:3],ceiling(n()/3))[1:n()]) %>%
  gather(., key = variable , value = value, -Species,-country)

This will gather all columns but Species and country (specified by the minus signs) and call the column containing the variable names 'variable' (the key ) and the entry 'value' (the value ).