replace duplicate values with NA in time series data using dplyr

Question

My data seems a bit different than other similar kind of posts.

box_num      date       x        y
1-Q      2018-11-18   20.2      8
1-Q      2018-11-25   21         


        

Answer 1

Here is an option with data.table. Convert the 'data.frame' to 'data.table' (setDT(df1), specify the columns of interest in .SDcols, replace the duplicated elements in the columns with NA and update those columns by assigning (:=) the output back to the columns

library(data.table)
setDT(df1)[,  c('x', 'y') := lapply(.SD, function(x) 
     replace(x, anyDuplicated(x), NA)), box_num, .SDcols= x:y]
df1
#   box_num       date      x      y
#1:     1-Q 2018-11-18 20.200  8.000
#2:     1-Q 2018-11-25 21.230  7.200
#3:     1-Q  2018-12-2     NA 23.000
#4:    98-L 2018-11-25  0.134  9.300
#5:    98-L  2018-12-2     NA  4.000
#6:   76-GI  2018-12-2 22.734  4.562
#7:   76-GI  2018-12-9 28.000     NA

data

df1 <- structure(list(box_num = c("1-Q", "1-Q", "1-Q", "98-L", "98-L", 
 "76-GI", "76-GI"), date = c("2018-11-18", "2018-11-25", "2018-12-2", 
"2018-11-25", "2018-12-2", "2018-12-2", "2018-12-9"), x = c(20.2, 
 21.23, 20.2, 0.134, 0.134, 22.734, 28), y = c(8, 7.2, 23, 9.3, 
 4, 4.562, 4.562)), class = "data.frame", 
 row.names = c(NA, -7L))

Answer 2

Using dplyr we can group_by box_num and use mutate_at x and y column and replace the duplicated value by NA.

library(dplyr)

df %>%
  group_by(box_num) %>%
  mutate_at(vars(x:y), funs(replace(., duplicated(.), NA)))


# box_num date          x     y
#  <fct>   <fct>      <dbl> <dbl>
#1 1-Q     2018-11-18 20.2    8   
#2 1-Q     2018-11-25 21.2    7.2 
#3 1-Q     2018-12-2  NA     23   
#4 98-L    2018-11-25  0.134  9.3 
#5 98-L    2018-12-2  NA      4   
#6 76-GI   2018-12-2  22.7    4.56
#7 76-GI   2018-12-9  28     NA  

---

A base R option (which might not be the best in this case) would be :

cols <- c("x", "y")
df[cols] <- sapply(df[cols], function(x) 
            ave(x, df$box_num, FUN = function(x) replace(x, duplicated(x), NA)))