计算过去 6 个月的独特观察次数（针对每次观察）

Question

How would you solve the following problem in R / tidyverse?:

sample data:

tibble(
  date = seq(as.Date(paste0("2010-01-",runif(1,1,25))), by = "month", length.out = 24),
  machine_ID = sample(letters[1:10],size = 24,replace = T),
  machine_cat = rep(c(1,2),12)
)

objective:

Add a column called last6m , which counts the number of unique machine_ID s observed in the last 6 months, within the associated machine_cat .

tidyverse and no looping is prefered (purrr is ok).

Appriciate if anyone would take a quick look: Thanks in advance :-)

Answer 1

The following solution was obtained based on the post suggested by MrFlick and r2evans: G. Grothendieck's answer

library(tidyverse)
library(lubridate)
library(sqldf)

data <- tibble(
  date = seq(as.Date(paste0("2010-01-",runif(1,1,25))), by = "month", length.out = 24),
  machine_ID = sample(letters[1:10],size = 24,replace = T),
  machine_cat = rep(c(1,2),12)
)

sqldf("
  SELECT a.*, COUNT(distinct(b.machine_ID)) AS last6m
  FROM data a
  LEFT JOIN data b
  ON a.machine_cat = b.machine_cat
  AND (b.date between a.date - 180 AND a.date)
  GROUP BY a.rowid
") %>% arrange(machine_cat,date)