Reshape multiple values at once

Question

I have a long data set I would like to make wide and I'm curious if there is a way to do this all in one step using the reshape2 or tidyr packages in R.

The data frame df looks like this:

id  type    transactions    amount
20  income       20          100
20  expense      25          95
30  income       50          300
30  expense      45          250

I'd like to get to this:

id  income_transactions expense_transactions    income_amount   expense_amount
20       20                           25                 100             95
30       50                           45                 300             250

I know I can get part of the way there with reshape2 via for example:

dcast(df, id ~  type, value.var="transactions")

But is there a way to reshape the entire df in one shot addressing both the "transactions" and "amount" variables at once? And ideally with new more appropriate column names?

Answer 1

In "reshape2", you can use recast (though in my experience, this isn't a widely known function).

library(reshape2)
recast(mydf, id ~ variable + type, id.var = c("id", "type"))
#   id transactions_expense transactions_income amount_expense amount_income
# 1 20                   25                  20             95           100
# 2 30                   45                  50            250           300

You can also use base R's reshape:

reshape(mydf, direction = "wide", idvar = "id", timevar = "type")
#   id transactions.income amount.income transactions.expense amount.expense
# 1 20                  20           100                   25             95
# 3 30                  50           300                   45            250

Or, you can melt and dcast, like this (here with "data.table"):

library(data.table)
library(reshape2)
dcast.data.table(melt(as.data.table(mydf), id.vars = c("id", "type")), 
                 id ~ variable + type, value.var = "value")
#    id transactions_expense transactions_income amount_expense amount_income
# 1: 20                   25                  20             95           100
# 2: 30                   45                  50            250           300

In later versions of dcast.data.table from "data.table" (1.9.8) you will be able to do this directly. If I understand correctly, what @Arun is trying to implement would be doing the reshaping without first having to melt the data, which is what happens presently with recast, which is essentially a wrapper for a melt + dcast sequence of operations.

---

And, for thoroughness, here's the tidyr approach:

library(dplyr)
library(tidyr)
mydf %>% 
  gather(var, val, transactions:amount) %>% 
  unite(var2, type, var) %>% 
  spread(var2, val)
#   id expense_amount expense_transactions income_amount income_transactions
# 1 20             95                   25           100                  20
# 2 30            250                   45           300                  50

Answer 2

With data.table v1.9.6+, we can cast multiple value.var columns simultaneously (and also use multiple aggregation functions in fun.aggregate). Please see ?dcast for more and also the examples section.

require(data.table) # v1.9.6+
dcast(dt, id ~ type, value.var=names(dt)[3:4])
#    id transactions_expense transactions_income amount_expense amount_income
# 1: 20                   25                  20             95           100
# 2: 30                   45                  50            250           300