Attach calendar effects to a tbl_now, and turn them into columns

These are the second and third steps of using calendar structure in a nowcast. First you write down which patterns you want with temporal_effects(); then:

add_temporal_effects() records that request on the object. Nothing is computed and no columns appear – the specification is stored lazily, so it survives filtering and joining without going stale.
compute_temporal_effects() materialises it, building one column per effect from the object's dates.

The split matters because the columns depend on the data. If you computed them first and then filtered, or changed the event-date column, the columns would silently describe the wrong rows. Recording the request and computing it at the end avoids that.

Call add_temporal_effects() more than once to accumulate several specifications on the same object; compute_temporal_effects() builds all of them.

Usage

add_temporal_effects(x, t_effects = NULL, overwrite = FALSE, ...)

# S3 method for class 'data.frame'
add_temporal_effects(
  x,
  t_effects = NULL,
  overwrite = FALSE,
  ...,
  date_col = NULL,
  numeric_col = NULL,
  name_prefix = paste0(".", date_col),
  weekend_days = c("Sat", "Sun")
)

# S3 method for class 'tbl_now'
add_temporal_effects(
  x,
  t_effects = NULL,
  overwrite = FALSE,
  ...,
  date_type = "event_date",
  weekend_days = c("Sat", "Sun")
)

compute_temporal_effects(x, overwrite = FALSE)

Arguments

x

A tbl_now object or a data.frame.

t_effects

A temporal_effects() object codifying the temporal effects to be used.

overwrite

Logical. When TRUE, columns that already exist are overwritten. When FALSE (the default) an existing column of the same name is an error, so an accidental second computation cannot silently replace your data.

...

Additional arguments (unused)

date_col

The column which contains the <Date> values from which effects will be calculated. This applies to all temporal_effects except for seasonal.

numeric_col

The column which contains the values from which the seasonal effects will be calculated. This applies only to seasonal effects. For date-related effects (such as month or day of the week) use date_col.

name_prefix

Character. Prefix for the names of the created columns.

weekend_days

A character or numeric vector defining which days count as the weekend. Defaults to Saturday and Sunday.

Character: day names or abbreviations, case-insensitive – c("Mon", "Tuesday", "wed", ...).
Numeric: integers 1-7 in lubridate::wday() numbering with week_start = 1, so 1 = Monday and 7 = Sunday.

date_type

Either event_date (default) or report_date to add temporal effects to those columns.

Value

add_temporal_effects() returns the object with the specification recorded. For a tbl_now no columns are added; for a plain data.frame, which has nowhere to record a specification, the columns are computed immediately.

compute_temporal_effects() returns a tbl_now with one column per effect appended. The specification is kept, so it still prints; the names of the columns just created are available from get_temporal_effect_cols().

Examples

data(denguedat)
dengue <- tbl_now(denguedat,
  event_date = "onset_week",
  report_date = "report_week",
  strata = "gender",
  verbose = FALSE
)

# Step 1-2: say you want a week-of-year effect, and record it.
dengue <- dengue |>
  add_temporal_effects(t_effects = temporal_effects(week_of_year = TRUE))

# The request is stored, but no column has been built yet.
get_temporal_effects(dengue)
#> [[1]]
#> [[1]]$t_effects
#> ── Temporal Effects ────────────────────────────────────────────────────────────
#> The following effects are in place:
#> • "week_of_year"
#> 
#> [[1]]$date_type
#> [1] "event_date"
#> 
#> [[1]]$weekend_days
#> [1] "Sat" "Sun"
#> 
#> 
get_temporal_effect_cols(dengue)
#> character(0)

# Step 3: materialise it.
computed <- compute_temporal_effects(dengue)
get_temporal_effect_cols(computed)
#> [1] ".event_week_of_year"
head(computed[[get_temporal_effect_cols(computed)[1]]])
#> [1] 1 1 1 1 1 1
#> 52 Levels: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 ... 52

# Specifications accumulate, so you can add a second pattern ...
both <- dengue |>
  add_temporal_effects(t_effects = temporal_effects(month_of_year = TRUE))
get_temporal_effect_cols(compute_temporal_effects(both))
#> [1] ".event_week_of_year"  ".event_month_of_year"

# ... swap the whole specification for another ...
dengue |>
  replace_temporal_effects(t_effects = temporal_effects(seasons = 52)) |>
  get_temporal_effects()
#> [[1]]
#> [[1]]$t_effects
#> ── Temporal Effects ────────────────────────────────────────────────────────────
#> The following effects are in place:
#> • "season" periods: 52
#> 
#> [[1]]$date_type
#> [1] "event_date"
#> 
#> [[1]]$weekend_days
#> [1] "Sat" "Sun"
#> 
#> 

# ... or forget it entirely.
dengue |>
  remove_temporal_effects() |>
  get_temporal_effects()
#> list()

Attach calendar effects to a `tbl_now`, and turn them into columns

Usage

Arguments

Value

See also

Examples