如何在 R 中创建具有下限的余额前滚(因此值不会低于 0)

Question

我正在编写一些代码来创建库存前滚，其中客户的期末余额不能低于零，但无法在R:中找到实现这一点的方法

ID
A		A		A		A		A

library(tidyverse)
df1 %>%
group_by(ID) %>%
mutate(EndBal = unlist(
accumulate2(c(0, Used), Purchased, ~..1 - ..2 + ..3)[-1]),
BegBal = lag(EndBal, default = 0))
ID    Purchased  Used EndBal BegBal
<chr>     <int> <int>  <dbl>  <dbl>
1 A             3     1      2      0
2 A             0     1      1      2
3 A             0     1      0      1
4 A             0     0      0      0
5 A             2     1      1      0

---

df1 <- structure(list(ID = c("A", "A", "A", "A", "A"), 
Purchased = c(3L, 0L, 0L, 0L, 2L),
Used = c(1L, 1L, 1L, 0L, 1L)), row.names = c(NA, -5L), class = "data.frame")

Answer 1

我使用了Onyambu发布的修改版本：

df1 <- structure(list(ID = c("A", "A", "A", "A", "A", "A"),
Purchased = c(3L, 0L, 0L, 0L, 0L, 2L)),
row.names = c(NA, -6L), class = "data.frame")

df2 <- df1 %>%
group_by(ID) %>%
mutate(EndBal = unlist(
accumulate(Purchased, ~..1 + ..2 - ifelse(..1 + ..2 > 0,1,0))),
BegBal = lag(EndBal, default = 0))

唯一的问题是它返回的EndBal值对于第一个记录来说太高了1