reshape data wide to long for multiple variables in R

Question

I have a dataset that shows each bank's investment and dollar value associated with this investment. Currently the data looks like this. I have inv and amt variables stretching from 1 to 43.

bankid year location inv1   amt1 inv2 amt2 ... inv43 amt43 
1          1990 NYC      AIG    2000 GM   4000     Ford  6000 

but I want the data to look like this

bankid year location inv number amt
1      1990  NYC     AIG  1     2000  
1      1990  NYC     GM   2     4000
...
1      1990  NYC     Ford 43    6000  

In Stata, I would use this code

reshape long inv amt, i(bankid location year) j(number)

What would be the equivalent code in R?

Answer 1

reshape can do this. Here I am using the posted subset of your data, where you have time variables 1, 2, and 43:

x <- read.table(header=TRUE, text='bankid year location inv1   amt1 inv2 amt2  inv43 amt43 
1          1990 NYC      AIG    2000 GM   4000     Ford  6000 ')
x
##   bankid year location inv1 amt1 inv2 amt2 inv43 amt43
## 1      1 1990      NYC  AIG 2000   GM 4000  Ford  6000

v <- outer(c('inv', 'amt'), c(1,2,43), FUN=paste0)
v
##      [,1]   [,2]   [,3]   
## [1,] "inv1" "inv2" "inv43"
## [2,] "amt1" "amt2" "amt43"

reshape(x, direction='long', varying=c(v), sep='')
##      bankid year location time  inv  amt id
## 1.1       1 1990      NYC    1  AIG 2000  1
## 1.2       1 1990      NYC    2   GM 4000  1
## 1.43      1 1990      NYC   43 Ford 6000  1

For your full table, the varying argument would be c(outer(c('inv', 'amt'), 1:43, FUN=paste0)) (but that won't work for the small example, as columns are missing).

Here, reshape infers the 'time' variable by inspecting the varying argument and finding common elements ( inv and amt ) on the left, and other elements on the right ( 1 , 2 , and 43 ). The sep argument says that there is no separator character (default sep character is . ).