CODEWITHSUNDEEP
r
pateljat
pateljat

Reputation: 23

Days Between Dates by Grouping (R)

I have a data set look like this:

ID | SKU | PurchaseDate
84 | TRP | 42027
84 | LTH | 42027
84 | IB229US | 42027
84 | IB229US | 42104

To load the above snippet as a data frame, the code is:

id<-c(84,84,84,84,84,84)
date<-c(42027, 42027, 42027, 42104, 42123, 42167)
SKU<- c("TRP", "LTH", "IB229US", "IB229US", "BTH", "IB229US")
data<-data.frame(id,date,SKU)

I'm trying to figure out average days between repurchase of the same SKU. Right now i'm able to find days between repurchase in general but not by SKU using:

data$dayssincelastpurchase<-unlist(by(data$date,data$ID,
                   function(x) c(NA,diff(x))))

How could i go about doing this?

Thanks

Upvotes: 1

Views: 1248

Answers (1)

cr1msonB1ade
cr1msonB1ade

Reputation: 1716

Here is a dplyr solution. First you arrange by date, then group by SKU and finally add the days since last SKU purchase.

library(dplyr)    
data <- data %>%
    arrange(date) %>%
    group_by(SKU) %>%
    mutate(dayssincelastpurchase=date - lag(date))

Upvotes: 6

Related Questions