How to convert array to data.table in R and back?

Question

is this the most straightforward way to convert an array into a data.table?

require(data.table)
require(ggplot2)

# this returns a data.tabl         


        

Answer 1

only works for versions 1.11.4 and 1.11.2 but not for some earlier versions

both approaches essentially return the same data.table but with A=1, B=2, C=3 in your second approach, and rows ordered in different ways. so the second approach is the way to go.

DT2 <- as.data.table(aaa)
head(DT2)
#   V1 V2 V3       value
#1:  1  1  1  0.32337516
#2:  1  1  2  1.59189589
#3:  1  2  1 -1.48751756
#4:  1  2  2 -0.86749305
#5:  1  3  1  0.01017255
#6:  1  3  2  2.66571093

#compare
DT[order(Freq), ]
#and 
DT2[order(value), ]