R - Comparing values in a column and creating a new column with the results of this comparison. Is there a better way than looping?

Question

I\'m a beginner of R. Although I have read a lot in manuals and here at this board, I have to ask my first question. It\'s a little bit the same as here but not really the s

Answer 1

You can use a "rolling equality test" with zoo 's rollapply. Also, identical is preferred to ==.

#identical(NA, NA)
#[1] TRUE
#NA == NA
#[1] NA

library(zoo)

df$mov <- c(rollapply(df$b, width = 2, 
        FUN = function(x) as.numeric(!identical(x[1], x[2]))), "no_comparison")
      #`!` because you want `0` as `TRUE` ;
      #I added a "no_comparison" to last value as it is not compared with any one
df
#   a  b           mov
#1  5  1             0
#2  1  1             0
#3  9  1             1
#4  5 NA             1
#5  9  1             1
#.....
#19 1 NA             0
#20 1 NA no_comparison