Fill downup updown

[coolbutuseless]

Add option to fill() to both fill-down-then-up and fill-up-then-down.

This is to replace a common idiom of mine, i.e.

df %>%
  group_by(group) %>%
  tidyr::fill(value, .direction = 'down') %>%
  tidyr::fill(value, .direction = 'up') %>%
  ungroup()

which could become

df %>%
  group_by(group) %>%
  tidyr::fill(value, .direction = 'downup') %>%
  ungroup()

Depending upon number of groups and number of variables to replace, the current duplicate call to fill() can be avoided, giving significant speed savings.

[hadley]

Can you explain why you'd want to do this?

[coolbutuseless]

A situation where I do this

I have values only known at some particular time and I need to fill this value both forwards and backwards in time.

A particular example

I work with clinical trial data, which is often provided in multiple files.

In the process of making a data set for analysis, particular information may only be recorded at certain events/times, but need to be filled forward/back in time throughout a related time period.

It is only valid to fill up/down within certain groupings (e.g. subjects, day, part of study) - with lots of subjects and lots of groups, this filling can take a noticeable amount of time.

Also filling may be done within different groupings for different variables.

A simplified concrete example:

suppressPackageStartupMessages({
  library(dplyr)
})

# Weight only recorded at event_type = 1, but considered
# valid across the entire event_num.
# If 'wt' not defined for a given event num, it may be
# carried forwards from a prior run, or backwards from a following run
df <- tibble::tribble(
  ~subject, ~time, ~event_type, ~event_num,  ~wt,
  1       ,     1,           0,          1,   NA,
  1       ,     2,           0,          1,   NA,
  1       ,     3,           1,          1,   20,
  1       ,     4,           0,          1,   NA,
  1       ,     5,           0,          1,   NA,
  1       ,     1,           0,          2,   NA,
  1       ,     2,           0,          2,   NA,
  1       ,     3,           1,          2,   NA,
  1       ,     4,           0,          2,   NA,
  1       ,     5,           0,          2,   NA,
  1       ,     1,           0,          3,   NA,
  1       ,     2,           0,          3,   NA,
  1       ,     3,           1,          3,   30,
  1       ,     4,           0,          3,   NA,
  1       ,     5,           0,          3,   NA,
)

# fill wt down/up within the event_num for each subject,
# then down/up within subject only.
df %>%
  group_by(subject, event_num) %>%
  tidyr::fill(wt, .direction = 'down') %>%
  tidyr::fill(wt, .direction = 'up'  ) %>%
  group_by(subject) %>%
  tidyr::fill(wt, .direction = 'down') %>%
  tidyr::fill(wt, .direction = 'up'  ) %>%
  ungroup()
#> # A tibble: 15 x 5
#>    subject  time event_type event_num    wt
#>      <dbl> <dbl>      <dbl>     <dbl> <dbl>
#>  1       1     1          0         1    20
#>  2       1     2          0         1    20
#>  3       1     3          1         1    20
#>  4       1     4          0         1    20
#>  5       1     5          0         1    20
#>  6       1     1          0         2    20
#>  7       1     2          0         2    20
#>  8       1     3          1         2    20
#>  9       1     4          0         2    20
#> 10       1     5          0         2    20
#> 11       1     1          0         3    30
#> 12       1     2          0         3    30
#> 13       1     3          1         3    30
#> 14       1     4          0         3    30
#> 15       1     5          0         3    30

Created on 2018-10-24 by the reprex
package (v0.2.0).

[echasnovski]

I also had several occasions where this type of functionality would be useful. However, I'd phrase them slightly differently: replace missing values based on the closest row (by some column, usually time). In case of an equal distance, use direction argument.

If data is ordered by reference column then these downup and updown solve this problem.

[coolbutuseless]

OK. I think i totally hosed this PR by trying to sync it with current master. :/

Burn to the ground and start again? I can't see a solution...

[hadley]

In the future, you might try usethis::pr_pull_source() which should do the right thing to get your branch synced back with master.