I've seen lots of questions like this but can't figure this simple problem out. I don't want to collapse the dataset. Say I have this dataset:
library(tidyverse)
library(lubridate)
df <- data.frame(group = c("a", "a", "a", "a", "a", "b", "b", "b"),
starts = c("2011-09-18", NA, "2014-08-08", "2016-09-18", NA, "2013-08-08", "2015-08-08", NA),
ends = c(NA, "2013-03-06", "2015-08-08", NA, "2017-03-06", "2014-08-08", NA, "2016-08-08"))
df$starts <- parse_date_time(df$starts, "ymd")
df$ends <- parse_date_time(df$ends, "ymd")
df
group starts ends
1 a 2011-09-18 <NA>
2 a <NA> 2013-03-06
3 a 2014-08-08 2015-08-08
4 a 2016-09-18 <NA>
5 a <NA> 2017-03-06
6 b 2013-08-08 2014-08-08
7 b 2015-08-08 <NA>
8 b <NA> 2016-08-08
Desired output is:
group starts ends epi
1 a 2011-09-18 <NA> 1
2 a <NA> 2013-03-06 1
3 a 2014-08-08 2015-08-08 2
4 a 2016-09-18 <NA> 3
5 a <NA> 2017-03-06 3
6 b 2013-08-08 2014-08-08 1
7 b 2015-08-08 <NA> 2
8 b <NA> 2016-08-08 2
I was thinking something like this but obviously doesn't account for episodes where there is no NA
df <- df %>%
group_by(group) %>%
mutate(epi = cumsum(is.na(ends)))
df
I'm not sure how to incorporate cumsum(is.na) with condition if_else. Maybe I'm going at it the wrong way?
Any suggestions would be great.
A solution using dplyr. Assuming your data frame is well structured that each start always has an associated end record.
df2 <- df %>%
group_by(group) %>%
mutate(epi = cumsum(!is.na(starts))) %>%
ungroup()
df2
# # A tibble: 8 x 4
# group starts ends epi
# <fct> <dttm> <dttm> <int>
# 1 a 2011-09-18 00:00:00 NA 1
# 2 a NA 2013-03-06 00:00:00 1
# 3 a 2014-08-08 00:00:00 2015-08-08 00:00:00 2
# 4 a 2016-09-18 00:00:00 NA 3
# 5 a NA 2017-03-06 00:00:00 3
# 6 b 2013-08-08 00:00:00 2014-08-08 00:00:00 1
# 7 b 2015-08-08 00:00:00 NA 2
# 8 b NA 2016-08-08 00:00:00 2