Shifting a column down by one

Question

Say I have a data.frame that looks like this

 df <- data.frame(AAA = rep(c(NA,sample(1:10, 1)),5),
  BBB = rep(c(NA,sample(1:10, 1)),5),
  CC         


        

Answer 1

Use a combination of the very efficient transform and na.omit functions

df <- na.omit(transform(df, CCC = c(NA, CCC[-nrow(df)])))