How to split a number into digits in R

Question

I have a data frame with a numerical ID variable which identify the Primary, Secondary and Ultimate Sampling Units from a multistage sampling scheme. I want to split the origina

Answer 1

Several neat answers have been made years ago, but a solution I find useful, using the outer function, has not been mentioned. In this age of search engines, I put it here in case others could find it handy.

I was faced with a slightly simpler problem: turning a column of 6-digit numbers into 6 columns representing each digit. This can be solved using a combination of outer, integer division (%/%) and modulo (%%).

 DF <- data.frame("ID" = runif(3)*10^6, "a" = sample(letters, 3,T))
 DF <- cbind(DF, "ID" = outer(DF$ID, 10^c(5:0), function(a, b) a %/% b %% 10))
 DF
#       ID a ID.1 ID.2 ID.3 ID.4 ID.5 ID.6
# 1 814895 z    8    1    4    8    9    5
# 2 417209 q    4    1    7    2    0    9
# 3 545797 c    5    4    5    7    9    7

The question asked here is slightly more complex, requiring different values for both integer division and modulo.

 DF <- data.frame("ID" = runif(3)*10^6, "a" = sample(letters, 3,T))
 DF <- cbind(DF, "ID" = outer(DF$ID, c(1:3), function(a,b) a %/% 10^c(5,3,0)[b] %% 10^b))
 DF
#      ID a ID.1 ID.2 ID.3
# 1 809372 q    8    9  372
# 2 954790 g    9   54  789
# 3 166970 l    1   66  969