aggregate by past dates (12 months) in R

Question

I am trying to summarise/aggregate data by date. For simplicity, I only need to do it for row 4 in the following data example. For example, the date in row 4 is "2014-06-06" (June 2014), so I want to sum Price and Vat (by Group_ID) for all dates in the last 12 months ie between 2013-06-01 and 2014-05-31 (ie, sum of row 1,2,3,6).

 Date       Price    Vat    Group_ID
 2014-01-10   705000  5023.00   A      
 2014-05-11   580000  6786.00   A       
 2014-05-19   333000  1809.84   A    
 2014-06-06   213000  1875.00   A (need result for this row only)     
 2014-06-21   310000  1905.96   B    
 2013-06-30   280000  3227.00   A
 2014-06-22   280000  3227.00   B
 2014-06-16   280000  3227.00   B
 2014-06-15   280000  3227.00   B
 2013-05-18   280000  3227.00   A    

The expected result for row 4 would be:

Date         S_Price   S_Vat      Group_ID
2014-06-06   1898000  16845.84     A  

Answer 1

You could use lubridate and between to create groups with target dates and then summarise the data frame. Here is my solution:

library(tidyverse)
library(lubridate)

df_2 <- df %>%
    mutate(target_date = case_when(
        between(Date,ymd("2013-06-01"),ymd("2014-05-31")) ~"2014-06-06",
        TRUE ~"0"
    )) %>%
    group_by(target_date, Group_ID) %>%
    summarise(S_price = sum(Price),
              S_Vat = sum(Vat)) %>%
    filter(target_date == "2014-06-06")

df_2