do() superseded! Alternative is to use across(), nest_by(), and summarise, how? - r

Question

I'm doing something quite simple. Given a dataframe of start dates and end dates for specific periods I want to expand/create a full sequence for each period binned by week (with the factor for each row), then output this in a single large dataframe.
For instance:
library(tidyverse)
library(lubridate)
# Dataset
start_dates = ymd_hms(c("2019-05-08 00:00:00",
"2020-01-17 00:00:00",
"2020-03-03 00:00:00",
"2020-05-28 00:00:00",
"2020-12-10 00:00:00",
"2021-05-07 00:00:00",
"2022-01-04 00:00:00"), tz = "UTC")
end_dates = ymd_hms(c( "2019-10-24 00:00:00",
"2020-03-03 00:00:00",
"2020-05-28 00:00:00",
"2020-12-10 00:00:00",
"2021-05-07 00:00:00",
"2022-01-04 00:00:00",
"2022-01-19 00:00:00"), tz = "UTC")
df1 = data.frame(studying = paste0("period",seq(1:7),sep = ""),start_dates,end_dates)
It was suggested to me to use do(), which currently works fine but I hate it when things are superseded. I also have a way of doing it using map2. But reading the file (https://dplyr.tidyverse.org/reference/do.html) suggests you can use nest_by(), across() and summarise() to do the same job as do(), how would I go about getting same result? I've tried a lot of things but I just can't seem to get it.
# do() way to do it
df1 %>%
group_by(studying) %>%
do(data.frame(week=seq(.$start_dates,.$end_dates,by="1 week")))
# transmute() way to do it
df1 %>%
transmute(weeks = map2(start_dates,end_dates, seq, by = "1 week"), studying)
%>% unnest(cols = c(weeks))

Answer 1

As the documentation of ?do suggests, we can now use summarise and replace the . with across():
library(tidyverse)
library(lubridate)
df1 %>%
group_by(studying) %>%
summarise(week = seq(across()$start_dates,
across()$end_dates,
by = "1 week"))
#> `summarise()` has grouped output by 'studying'. You can override using the
#> `.groups` argument.
#> # A tibble: 134 x 2
#> # Groups: studying [7]
#> studying week
#> <chr> <dttm>
#> 1 period1 2019-05-08 00:00:00
#> 2 period1 2019-05-15 00:00:00
#> 3 period1 2019-05-22 00:00:00
#> 4 period1 2019-05-29 00:00:00
#> 5 period1 2019-06-05 00:00:00
#> 6 period1 2019-06-12 00:00:00
#> 7 period1 2019-06-19 00:00:00
#> 8 period1 2019-06-26 00:00:00
#> 9 period1 2019-07-03 00:00:00
#> 10 period1 2019-07-10 00:00:00
#> # … with 124 more rows
Created on 2022-01-19 by the reprex package (v0.3.0)

Answer 2

You can also use tidyr::complete:
df1 %>%
group_by(studying) %>%
complete(start_dates = seq(from = start_dates, to = end_dates, by = "1 week")) %>%
select(-end_dates, weeks = start_dates)
# A tibble: 134 x 2
# Groups: studying [7]
studying weeks
<chr> <dttm>
1 period1 2019-05-08 00:00:00
2 period1 2019-05-15 00:00:00
3 period1 2019-05-22 00:00:00
4 period1 2019-05-29 00:00:00
5 period1 2019-06-05 00:00:00
6 period1 2019-06-12 00:00:00
7 period1 2019-06-19 00:00:00
8 period1 2019-06-26 00:00:00
9 period1 2019-07-03 00:00:00
10 period1 2019-07-10 00:00:00
# ... with 124 more rows

Answer 3

Although marked Experimental the help file for group_modify does say that
‘group_modify()’ is an evolution of ‘do()’
and, in fact, the code for the example in the question using group_modify is nearly the same as with do.
# with group_modify
df2 <- df1 %>%
group_by(studying) %>%
group_modify(~ data.frame(week = seq(.$start_dates, .$end_dates, by = "1 week")))
# with do
df0 <- df1 %>%
group_by(studying) %>%
do(data.frame(week = seq(.$start_dates, .$end_dates, by = "1 week")))
identical(df2, df0)
## [1] TRUE

Answer 4

Not sure if this exactly what you are looking for, but here is my attempt with rowwise and unnest
df1 %>%
rowwise() %>%
mutate(week = list(seq(start_dates, end_dates, by = "1 week"))) %>%
select(studying, week) %>%
unnest(cols = c(week))

Answer 5

Another approach:
library(tidyverse)
df1 %>%
group_by(studying) %>%
summarise(df = tibble(weeks = seq(start_dates, end_dates, by = 'week'))) %>%
unnest(df)
#> `summarise()` has grouped output by 'studying'. You can override using the `.groups` argument.
#> # A tibble: 134 × 2
#> # Groups: studying [7]
#> studying weeks
#> <chr> <dttm>
#> 1 period1 2019-05-08 00:00:00
#> 2 period1 2019-05-15 00:00:00
#> 3 period1 2019-05-22 00:00:00
#> 4 period1 2019-05-29 00:00:00
#> 5 period1 2019-06-05 00:00:00
#> 6 period1 2019-06-12 00:00:00
#> 7 period1 2019-06-19 00:00:00
#> 8 period1 2019-06-26 00:00:00
#> 9 period1 2019-07-03 00:00:00
#> 10 period1 2019-07-10 00:00:00
#> # … with 124 more rows
Created on 2022-01-20 by the reprex package (v2.0.1)