Count with conditions in R dataframe

问题

I have the following DF:

    Week   SKU   Discount(%)
     1     111       5
     2     111       5
     3     111       0
     4     111      10
     1     222       0
     2     222      10
     3     222      15
     4     222      20
     1     333       5
     2     333       0
     3     333       0

I would like to have this outcome:

    Week   SKU   Discount(%)   Duration  LastDiscount
     1     111       5            2           0
     2     111       5            2           0
     3     111       0            0           0
     4     111      10            1           2
     1     222       0            0           0
     2     222      10            3           0
     3     222      15            3           0
     4     222      20            3           0
     1     333       5            1           0
     2     333       0            0           0
     3     333       0            0           0

Duration is the number of weeks that 1 SKU had discounts continuously. LastDiscount counts the number of weeks from the last time the SKU was on a continuous discount, only if there are weeks with 0 in between discounts.

回答1:

One option to check the "Duration' is after grouping by 'SKU', use rle (run-length-encoding) on a logical vector, gets the lengths and 'values' and replicate those duration. Similarly, the "LastDiscount" can be obtained by getting the sum of logical values

library(dplyr)
df1 %>%
  group_by(SKU) %>% 
  mutate(Duration = with(rle(Discount > 0), rep(lengths*values, 
        lengths)),
         temp = with(rle(Discount > 0), sum(values != 0)), 
         LastDiscount = if(temp[1] > 1) c(rep(0, n()-1), temp[1]) else 0) %>%
  select(-temp)
# A tibble: 11 x 5
# Groups:   SKU [3]
#    Week   SKU Discount Duration LastDiscount
#   <int> <int>    <int>    <int>        <dbl>
# 1     1   111        5        2            0
# 2     2   111        5        2            0
# 3     3   111        0        0            0
# 4     4   111       10        1            2
# 5     1   222        0        0            0
# 6     2   222       10        3            0
# 7     3   222       15        3            0
# 8     4   222       20        3            0
# 9     1   333        5        1            0
#10     2   333        0        0            0
#11     3   333        0        0            0

---

Or using data.table

library(data.table)
i1 <- setDT(df1)[, grp := rleid(Discount > 0), SKU][Discount > 0,
  Duration := .N,  .(grp, SKU)][, 
   LastDiscount := uniqueN(grp[Discount > 0]), .(SKU)][, 
   tail(.I[Discount > 0 & LastDiscount > 1], 1), SKU]$V1
df1[-i1, LastDiscount := 0][]

data

df1 <- structure(list(Week = c(1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 
3L), SKU = c(111L, 111L, 111L, 111L, 222L, 222L, 222L, 222L, 
333L, 333L, 333L), Discount = c(5L, 5L, 0L, 10L, 0L, 10L, 15L, 
20L, 5L, 0L, 0L)), class = "data.frame", row.names = c(NA, -11L
))

来源：https://stackoverflow.com/questions/59204544/count-with-conditions-in-r-dataframe