refOpts: Define 'ref.x' or 'ref.y' options for 'openair' plots

In openair: Tools for the Analysis of Air Pollution Data

Define ref.x or ref.y options for openair plots

Description

This function provides a convenient way to set default options for ref.x or ref.y layers in openair plots, which show some form of horizontal or vertical reference line. intercept can be a vector of any length; all other arguments will be recycled to be equal to that length.

Usage

refOpts(
  intercept,
  alpha = 1,
  colour = "black",
  linetype = 1,
  linewidth = 1,
  color = NULL
)

Arguments

intercept	The axis intercept(s) for the reference lines. Should be numeric, dates, or date-times depending on the axis types. If another data type is provided, it will attempt to be coerced to the correct type using as.numeric(), lubridate::as_date() or lubridate::as_datetime(), respectively.
alpha	Numeric value between 0 and 1 specifying the transparency of the lines. Default is 1 (fully opaque).
colour, color	Colour of the lines. Default is "black". colour and color are interchangeable, but colour is used preferentially if both are given.
linetype	Line type. Can be an integer (e.g., 1 for solid, 2 for dashed) or a string (e.g., "solid", "dashed"). Default is 1 (solid).
linewidth	Numeric value specifying the width of the lines. Default is 1.

Value

A list of options that can be passed to the ref.x or ref.y arguments of functions like timePlot().

Examples

# `ref.y` can just be a value to plot
timePlot(mydata, avg.time = "month", ref.y = 250, ref.x = "2002/01/01")

# use the `refOpts()` function to customise reference lines
timePlot(
  mydata,
  avg.time = "month",
  ref.y = refOpts(
    c(250, 300),
    alpha = c(0.5, 1),
    colour = c("grey50", "blue"),
    linetype = c(2, 1),
    linewidth = c(1, 2)
  )
)

openair documentation built on May 20, 2026, 5:07 p.m.