How to perform a join based on intervals with dplyr?

问题

I have a data frame containing two columns: a grouping variable and a interval period over which the grouping variable holds. I have another data frame with a date column and a value column. How can I join these two tables together somewhat efficiently with dplyr+tidyverse functions?

library(dplyr)
library(lubridate)
ty <- data_frame(date = mdy(paste(1, 1 + seq(20), 2017, sep = "/")), 
                 y = c(rnorm(7), rnorm(7, mean = 2), rnorm(6, mean = -1)))
gy <- data_frame(period = interval(mdy(c("01/01/2017", "01/08/2017", "01/15/2017")), 
                                   mdy(c("01/07/2017", "01/14/2017", "01/20/2017"))), 
                          batch = c(1, 2, 3))

I want to build the table that is equivalent to:

ty %>% mutate(batch = c(rep(1, 7), rep(2, 7), rep(3, 6)))

Ideally, this should work reasonably quickly on data sets of up to 1,000,000 rows. Better still if it works on 100,000,000 :).

回答1:

~~How about:~~

ty %>% 
  mutate(batch = case_when(
  ty$date %within% gy$period[1] ~gy$batch[1],
  ty$date %within% gy$period[2] ~gy$batch[2],
  ty$date %within% gy$period[3] ~gy$batch[3]))

~~You would obviously need to define the case_when intervals. How many have you got? I've used cat and paste0 with good effect for that in the past.~~

Edited to reflect OP's comments. This should take care of the NSE and would allow the generation of the case_when intervals programatically:

ty %>%
  mutate(batch = eval(parse(text = paste0("case_when(",
                                      paste(
                                        paste0(
                                          "ty$date %within% gy$period[",
                                          seq_along(gy$period),
                                          "] ~gy$batch[",
                                          seq_along(gy$period),
                                          "]"
                                        ),
                                        collapse = ", "
                                      ), ")"))))

回答2:

This is the best I could come up with so far:

ty$batch <- unlist(lapply(ty$date, function(d) gy$batch[which(d %within% gy$period)]), recursive = FALSE, use.names = FALSE)

But it doesn't seem very fast.

来源：https://stackoverflow.com/questions/44398318/how-to-perform-a-join-based-on-intervals-with-dplyr

标签

dplyr

lubridate