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Fill in missing values with previous or next value

Source: R/fill.R
fill.dtplyr_step.Rd

This is a method for the tidyr fill() generic. It is translated to data.table::nafill(). Note that data.table::nafill() currently only works for integer and double columns.

Usage

# S3 method for dtplyr_step
fill(data, ..., .direction = c("down", "up", "downup", "updown"))

Arguments

data

A data frame.

...

<tidy-select> Columns to fill.

.direction

Direction in which to fill missing values. Currently either "down" (the default), "up", "downup" (i.e. first down and then up) or "updown" (first up and then down).

Examples

library(tidyr)

# Value (year) is recorded only when it changes
sales <- lazy_dt(tibble::tribble(
  ~quarter, ~year, ~sales,
  "Q1",    2000,    66013,
  "Q2",      NA,    69182,
  "Q3",      NA,    53175,
  "Q4",      NA,    21001,
  "Q1",    2001,    46036,
  "Q2",      NA,    58842,
  "Q3",      NA,    44568,
  "Q4",      NA,    50197,
  "Q1",    2002,    39113,
  "Q2",      NA,    41668,
  "Q3",      NA,    30144,
  "Q4",      NA,    52897,
  "Q1",    2004,    32129,
  "Q2",      NA,    67686,
  "Q3",      NA,    31768,
  "Q4",      NA,    49094
))

# `fill()` defaults to replacing missing data from top to bottom
sales %>% fill(year)
#> Source: local data table [16 x 3]
#> Call:   copy(`_DT10`)[, `:=`(year = nafill(year, "locf"))]
#> 
#>   quarter  year sales
#>   <chr>   <dbl> <dbl>
#> 1 Q1       2000 66013
#> 2 Q2       2000 69182
#> 3 Q3       2000 53175
#> 4 Q4       2000 21001
#> 5 Q1       2001 46036
#> 6 Q2       2001 58842
#> # … with 10 more rows
#> 
#> # Use as.data.table()/as.data.frame()/as_tibble() to access results

# Value (n_squirrels) is missing above and below within a group
squirrels <- lazy_dt(tibble::tribble(
  ~group,    ~name,     ~role,     ~n_squirrels,
  1,      "Sam",    "Observer",   NA,
  1,     "Mara", "Scorekeeper",    8,
  1,    "Jesse",    "Observer",   NA,
  1,      "Tom",    "Observer",   NA,
  2,     "Mike",    "Observer",   NA,
  2,  "Rachael",    "Observer",   NA,
  2,  "Sydekea", "Scorekeeper",   14,
  2, "Gabriela",    "Observer",   NA,
  3,  "Derrick",    "Observer",   NA,
  3,     "Kara", "Scorekeeper",    9,
  3,    "Emily",    "Observer",   NA,
  3, "Danielle",    "Observer",   NA
))

# The values are inconsistently missing by position within the group
# Use .direction = "downup" to fill missing values in both directions
squirrels %>%
  dplyr::group_by(group) %>%
  fill(n_squirrels, .direction = "downup") %>%
  dplyr::ungroup()
#> Source: local data table [12 x 4]
#> Call:   copy(`_DT12`)[, `:=`(n_squirrels = nafill(nafill(n_squirrels, 
#>     "locf"), "nocb")), by = .(group)]
#> 
#>   group name    role        n_squirrels
#>   <dbl> <chr>   <chr>             <dbl>
#> 1     1 Sam     Observer              8
#> 2     1 Mara    Scorekeeper           8
#> 3     1 Jesse   Observer              8
#> 4     1 Tom     Observer              8
#> 5     2 Mike    Observer             14
#> 6     2 Rachael Observer             14
#> # … with 6 more rows
#> 
#> # Use as.data.table()/as.data.frame()/as_tibble() to access results

# Using `.direction = "updown"` accomplishes the same goal in this example