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Position scales for continuous data (x & y) with labelled vertical/horizontal markers

scale_limitval.Rd

This function is a wrapper around ggplot2::scale_x_continuous() or ggplot2::scale_y_continuous() which allows users to automatically draw labelled horizontal or vertical markers at specified points. In the air quality world, this may be particularly useful to display limit values, such as those defined in legislation or recommended by health authorities.

Usage

scale_y_limitval(
  marker_values,
  marker_colours = "black",
  marker_labels = marker_values,
  marker_linetypes = 2,
  trans = "identity",
  ...
)

scale_x_limitval(
  marker_values,
  marker_colours = "black",
  marker_labels = marker_values,
  marker_linetypes = 2,
  trans = "identity",
  ...
)

Arguments

marker_values

Numeric vector of values at which to draw marker lines.

marker_colours

Character vector of colours for marker lines. Should be the same length as marker_values.

marker_labels

Character vector of labels for marker lines. Should be the same length as marker_values. Defaults to using the numeric values given in marker_values.

marker_linetypes

Vector of values for marker linetypes. Should be the same length as marker_values. Defaults to dashed lines (2).

trans

The name of a transformation object. See ggplot2::scale_x_continuous() for more information.

...

Other arguments to pass to ggplot2::scale_x_continuous()/ggplot2::scale_y_continuous().

Details

This function uses ggplot2::sec_axis() to display the line labels. One can therefore not pass ggplot2::sec_axis() to .... If users wish to use ggplot2::sec_axis() it is recommended to use ggplot2::geom_abline() to draw lines manually.

Unlike other "scale" functions the order in which this function is added to the ggplot2::ggplot() object matters. Adding scale_*_limitval() after ggplot2::geom_line() will draw the line markers on top of the trend line, whereas adding it before will draw the markers below.