rdata.tablereshape2meltdcast

reshape from wide to long, simple data.table issue


I know there must be a one-line data.table solution for this, probably with dcast, but I can't figure it out.

I have data like this:

library(data.table)
data1 <- data.table(
  id = seq(1:5),
  code = c("A","A","B","A","B"),
  date = as.Date( c("2021-08-11","2021-01-05","2021-02-18","2021-02-13","2021-12-13" ))
)
data2 <- data.table(
  id = seq(1:5),
  code = c("B","B","A","B","A"),
  date = as.Date( c("2021-08-13","2021-01-05","2021-02-19","2021-02-14","2021-12-13" ))
)
data3 <- rbind(data1, data2)

I simply wish to reshape to a wide format like this

data_want <- data.table(
  id = seq(1:5),
  code1 = c("A", "A","B","A","B"),
  data1 = c("2021-08-11", "2021-01-05","2021-02-18","2021-02-13","2021-12-13"),
  code2 = c("B", "B","A","B","A"),
  data2 = c("2021-08-13", "2021-01-05","2021-02-19","2021-02-14","2021-12-13")
)

How to do it with dcast?


Solution

  • You could also make use of rowid as follows

    dcast(data3, id ~ rowid(id), value.var = c("code", "date"))
    #   id code_1 code_2     date_1     date_2
    #1:  1      A      B 2021-08-11 2021-08-13
    #2:  2      A      B 2021-01-05 2021-01-05
    #3:  3      B      A 2021-02-18 2021-02-19
    #4:  4      A      B 2021-02-13 2021-02-14
    #5:  5      B      A 2021-12-13 2021-12-13