Plot a nowcast

Draws a fan chart of a tbl_nowcast: the counts reported so far as grey columns, one shaded band per central prediction interval over them, and the median as a line, so that the size of the correction the model is applying is visible as the gap between the bars and the fan.

Arguments

object

A tbl_nowcast object.

...

Unused; present for compatibility with ggplot2::autoplot().

levels

Numeric vector of central interval widths to shade. Defaults to the widest intervals available in the object.

show_reported

Logical. Whether to draw the cases reported so far as columns under the fan – get_latest_reported_cases() on the object's own source data, so the bars are what the model was actually shown as of now, not what those dates eventually reached. The vertical gap between the top of a bar and the fan is the correction the nowcast is making, which is the whole reason to draw it. Requires the nowcast to carry its source data.

The bars are one period wide, taken from get_event_units(). A fixed width would draw hairlines on a weekly series, and one wider than the step would make ggplot2 stack overlapping bars, so each would show several periods' counts rather than its own.

colour

Colour of the fan. Defaults to the tbl.now palette's green: a nowcast is an estimate of the epidemic process (cases by event date), which the package always draws in green, with red reserved for the reporting process.

Value

A ggplot object.

See also

run_nowcast(), nowcast_ensemble()

Examples

predictions <- tidyr::expand_grid(
  onset_week = as.Date("2020-01-05") + seq(0, 28, by = 7),
  .quantile_level = c(0.05, 0.25, 0.5, 0.75, 0.95)
)
predictions$.value <- 10 + 30 * predictions$.quantile_level
nc <- tbl_nowcast(predictions = predictions, method = "toy", event_date = "onset_week")

autoplot(nc)