Reshape multiple values at once

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.

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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