How to create id variable by grouping sequenced numbers?

Question

I want to add ID variable in this data. If receipt_ids are sequenced numbers, then those have same IDs.

CUST_NO_ID  receipt_id      dollar
  12         29               


        

Answer 1

Assuming your data frame has already been sorted by CUST_NO_ID and receipt_id, you can use cumsum on a conditional vector where TRUE indicates the position a new ID should be created:

df$ID = cumsum(c(T, diff(df$receipt_id) != 1 | diff(df$CUST_NO_ID) != 0)))

df
#   CUST_NO_ID receipt_id dollar ID
#1          12         29  20.84  1
#2          12         30  20.21  1
#3          12         86  24.50  2
#4          12         87  20.68  2
#5          12        108  25.79  3
#6          12        109  24.93  3
#7          12        125  20.63  4
#8          12        126   9.90  4
#9          19        193  69.48  5
#10         19        194  46.88  5

Answer 2

Had a similar notion to @Psidom, but he beat me to the punch with cumsum. Here's a dplyr solution. Adding in group_by can give you added flexibility if you want to restart ids by customer number.

df %>% 
  mutate(id = cumsum(c(TRUE, diff(receipt_id) != 1)))

Answer 3

We can use data.table

library(data.table)
setDT(df)[, id := cumsum(c(TRUE, diff(receipt_id)!=1))]

Or use the shift

setDT(df)[, id := cumsum((receipt_id - shift(receipt_id, fill=receipt_id[1]))!=1)]

Answer 4

This does it

id <- 1

for(row in 1:nrow(data)){
  if(row == 1){
    dif <- 1
  }else{
    dif <- data[row,'receipt_id'] - data[row-1,'receipt_id']
  }

  if(dif != 1){
    id = id + 1
  }

  data[row,'ID'] = id
}