How to convert a data frame to a 3d array in R

Question

I have a data frame that I want to convert to a three-dimensional array. One of the columns in the data frame should serve as the grouping variable for splitting the frame i

Answer 1

Here is what I'd probably do:

library(abind)
abind(split(df, df$i), along=3)
# , , 1
# 
#   i x y           l
# 5 1 0 0 -0.56047565
# 6 1 0 1 -0.23017749
# 7 1 1 0  1.55870831
# 8 1 1 1  0.07050839
# 
# , , 2
# 
#   i x y          l
# 5 2 0 0  0.1292877
# 6 2 0 1  1.7150650
# 7 2 1 0  0.4609162
# 8 2 1 1 -1.2650612