Cumulative sum in a window (or running window sum) based on a condition in R

Question

I am trying to calculate cumulative sum for a given window based on a condition. I have seen threads where the solution does conditional cumulative sum (Calculate a conditio

Answer 1

Not a new tidyverse answer but I think nest helps with readability

library(tidyverse)
library(zoo)

roll_cumsum <- function(df) {
                  df %>%
                     complete(FY = full_seq(FY, period=1)) %>%
                     mutate(roll_cumsum = rollapplyr(Rev, 5, sum, na.rm=TRUE, partial=TRUE))
               }

DFI %>%
  group_by_at(vars(-Rev)) %>%
  summarise(Rev = sum(Rev)) %>%
  group_by(Customer, Product) %>%
  nest(FY, Rev) %>%
  mutate(data = map(data, ~roll_cumsum(.x))) %>%
  unnest() %>%
  filter(!is.na(Rev)) %>%
  arrange(Customer, Product, FY)

# A tibble: 16 x 5
   # Customer Product    FY   Rev roll_cumsum
      #             
 # 1    13575 A        2011  4.00        4.00
 # 2    13575 A        2012  3.00        7.00
 # 3    13575 A        2013  3.00       10.0 
 # 4    13575 A        2015  1.00       11.0 
 # 5    13575 A        2016  2.00        9.00
 # 6    13575 B        2011  3.00        3.00
 # 7    13575 B        2012  3.00        6.00
 # 8    13575 B        2013  4.00       10.0 
 # 9    13575 B        2014  5.00       15.0 
# 10    13575 B        2015  6.00       21.0 
# 11    13578 A        2010  3.00        3.00
# 12    13578 A        2016  2.00        2.00
# 13    13578 B        2013  2.00        2.00
# 14    13578 C        2014  4.00        4.00
# 15    13578 D        2015  2.00        2.00
# 16    13578 E        2010  2.00        2.00