I don't know whether this is an integer64 (from bit64) problem, or a melt problem (from reshape2, but if I try to reshape a data.frame containing integer64 data then the class information is destroyed in the process and it reverts to the double representation:
library(bit64)
library(reshape2)
DF = data.frame(I =letters, Num1 = as.integer64(1:26), Num2 = as.integer64(1:26))
DFM = melt(DF, id.vars = "I")
sapply(DF, class)
sapply(DFM, class)
gives:
> sapply(DF, class)
I Num1 Num2
"factor" "integer64" "integer64"
> sapply(DFM, class)
I variable value
"factor" "factor" "numeric"
And because integer64 is double underneath, the data is "corrupted"
> DF
I Num1 Num2
1 a 1 1
2 b 2 2
3 c 3 3
4 d 4 4
5 e 5 5
...
> DFM
I variable value
1 a Num1 4.940656e-324
2 b Num1 9.881313e-324
3 c Num1 1.482197e-323
4 d Num1 1.976263e-323
5 e Num1 2.470328e-323
6 f Num1 2.964394e-323
What is causing this? Is this a integer64 problem or a melt problem? When creating classes what can be done to avoid this sort of thing?
It seems to be a limitation of the package which is also mentioned in their documentation here on page 9. For example:
x <- data.frame(a=as.integer64(1:5), b=as.integer64(1:5))
> x
# a b
# 1 1 1
# 2 2 2
# 3 3 3
# 4 4 4
# 5 5 5
> unlist(x)
# a1 a2 a3 a4 a5 b1
# 4.940656e-324 9.881313e-324 1.482197e-323 1.976263e-323 2.470328e-323 4.940656e-324
# b2 b3 b4 b5
# 9.881313e-324 1.482197e-323 1.976263e-323 2.470328e-323
> as.matrix(x)
# a b
# [1,] 4.940656e-324 4.940656e-324
# [2,] 9.881313e-324 9.881313e-324
# [3,] 1.482197e-323 1.482197e-323
# [4,] 1.976263e-323 1.976263e-323
# [5,] 2.470328e-323 2.470328e-323
x <- as.integer64(1:5)
> is.vector(x)
# [1] FALSE
> as.vector(x)
# [1] 4.940656e-324 9.881313e-324 1.482197e-323 1.976263e-323 2.470328e-323