dataframe - R and dplyr : how to use values from a previous row and column -


i trying create new variable function of previous rows , columns. have found lag() function in dplyr can't accomplish like.

library(dplyr) x = data.frame(replicate(2, sample(1:3,10,rep=true)))     x1 x2 1   1  3 2   2  3 3   2  2 4   1  3 5   2  3 6   2  1 7   3  2 8   1  1 9   1  3 10  2  2  x = mutate(x, new_col = # if x2==1, value of x1 in previous row,                         # if x2!=1, 0))

my best attempt:

foo = function(x){     if (x==1){         return(lag(x1))     }else{         return(0) }  x = mutate(x, new_col=foo(x1))

we can use ifelse

x %>%    mutate(newcol = ifelse(x2==1, lag(x1), 0))

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