Seasonal-subseries (cycle) plot

Draws a seasonal-subseries plot (also called a cycle plot): the series is split into one small panel per season (e.g. one panel per calendar month for monthly data), and within each panel the value is drawn across successive cycles (e.g. across years). A horizontal reference line in every panel marks that season's mean. This makes the seasonal pattern (differences between panels) and the within-season trend over time (the slope inside each panel) visible at the same time, which a single overlaid line cannot show.

Usage

seasonal_plot(
  x,
  frequency = NULL,
  style = c("subseries", "season"),
  season_labels = NULL,
  means = TRUE,
  point = TRUE,
  palette = NULL,
  title = NULL,
  x_lab = NULL,
  y_lab = NULL
)

Arguments

x

A ts object, or a numeric vector (then frequency is required), holding one series. A multivariate ts or a matrix with several columns is refused.

frequency

Number of observations per period (e.g. 12 for monthly data); taken from x when it is a ts. A frequency that is not a whole number, such as the 365.25 / 7 of weekly data, is rounded down to whole seasons, as stats::stl() rounds it, and a message says so. The seasons are then counted from the first observation.

style

"subseries" for the faceted cycle plot (one panel per season) or "season" for one line per cycle across the seasons.

season_labels

Optional character vector of length frequency giving the season (panel/axis) labels, e.g. month.abb. When NULL (default) sensible labels are inferred (month abbreviations for frequency 12, quarter labels for frequency 4, otherwise the season index).

means

Whether to draw the per-season mean reference line (style = "subseries" only).

point

Whether to add points as well as the connecting line.

palette

Colours used for the cycle lines when style = "season". Defaults to a blue ramp from #4a8fc0 through the brand blue to #08315a, whose palest colour has a contrast of 3.51:1 against white. The sequential ramp of depictr_palette() starts paler, at #e6eff5, which suits a fill but leaves a line close to invisible.

title, x_lab, y_lab

Title and axis labels.

Value

A ggplot2::ggplot object.

Details

Two layouts are offered. With style = "subseries" (the default) the panels are faceted side by side, each tracing one season across cycles: the classic Cleveland cycle plot, matching feasts::gg_subseries(). With style = "season" every cycle is drawn as its own line over the seasons on a shared axis (the seasonal-plot layout of forecast::ggseasonplot()), which is handy for spotting an unusual year. The lines run from a mid blue for the first cycle to a dark blue for the last, so they read in time order. Past about six cycles, neighbouring cycles take colours too close to tell apart, and the colours then show the order of the cycles more than which is which. When individual cycles must be told apart, use style = "subseries", where each cycle keeps its own place on the axis of every panel, or plot fewer cycles.

See also

decompose_plot(), timeseries_plot()

Examples

# Monthly air passengers: rising within-month trend, summer peak
seasonal_plot(AirPassengers)

seasonal_plot(AirPassengers, style = "season")