Axis handling helper functions

`abbr_years()` is a helper functions that allows users to abbreviate year labels to their two-digit representation (e.g., 2008 to '08), but not abbreviate any specified breaks. It does so by creating a new function that takes the breaks supplied by ggplot2 as its only argument. The function was modeled after the syntax and approach of the labeling functions in the scales::label_* family.

abbr_years(full_by_pos = c(1), full_by_year = NULL, dateaxis = FALSE)

Arguments

full_by_pos

Vector of integers, the position of breaks that should not be abbreviated. This defaults to c(1), which retains the original first label and abbreviates subsequent ones. If all breaks should be abbreviated, this can be set to NULL.

full_by_year

Vector of integers, the value of breaks that should not be abbreviated. Defaults to NULL.

dateaxis

Bool. FALSE, the default, directs the function to treat the breaks as integers. If set to TRUE the function will instead treat the breaks as date objects. TRUE should be used when called within a scale_*_date ggplot element.

Examples

# basic functionality
abbr_years()(c(2010:2020))
#>  [1] "2010" "'11"  "'12"  "'13"  "'14"  "'15"  "'16"  "'17"  "'18"  "'19" 
#> [11] "'20" 
abbr_years(full_by_year = 2000)(c(1990:2010))
#>  [1] "1990" "'91"  "'92"  "'93"  "'94"  "'95"  "'96"  "'97"  "'98"  "'99" 
#> [11] "2000" "'01"  "'02"  "'03"  "'04"  "'05"  "'06"  "'07"  "'08"  "'09" 
#> [21] "'10" 


# Default implementation - this will abbreviate all labels except the first
# for both continuous and date scales.

df2 <- dplyr::mutate(transit_ridership, year2 = as.Date(lubridate::date_decimal(year)))
df1 <- dplyr::filter(df2, year >= 2000)

ggplot(df1,
       aes(x = year, y = ridership, color = system)) +
  geom_line() +
  scale_x_continuous(labels = abbr_years())
#> Warning: Removed 7 rows containing missing values or values outside the scale range
#> (`geom_line()`).


ggplot(df1,
       aes(x = year2, y = ridership, color = system)) +
  geom_line() +
  scale_x_date(labels = abbr_years(dateaxis = TRUE))
#> Warning: Removed 7 rows containing missing values or values outside the scale range
#> (`geom_line()`).


# If customizations are desired, users can use \code{full_by_pos} and/or
# \code{full_by_year} to maintain the full version of the specified labels.

ggplot(df2,
       aes(x = year2, y = ridership, color = system)) +
  geom_line() +
  scale_x_date(labels = abbr_years(full_by_year = c(2000), dateaxis = TRUE))
#> Warning: Removed 27 rows containing missing values or values outside the scale range
#> (`geom_line()`).


# You can also remove the default maintenance of the first label and only
# specify specific years.
ggplot(df2,
       aes(x = year, y = ridership, color = system)) +
  geom_line() +
  scale_x_continuous(labels = abbr_years(full_by_pos = NULL,
                                         full_by_year = c(1990,2020)))
#> Warning: Removed 27 rows containing missing values or values outside the scale range
#> (`geom_line()`).