Slide styling for a grouped plot, in one reusable object

You already know the two-step shape of a hvtiPlotR figure: a constructor prepares and validates the data, plot() hands back a bare ggplot, and you finish it with +. Across a deck that finishing step is the same few lines on every slide, and copying them plot by plot is how one figure quietly drifts out of step with the rest.

hv_ppt_series() bundles the finishing step into a single object you add once per plot. It carries the PowerPoint theme, a color scale and a matching shape scale, so a whole deck takes its look from one definition.

Usage

hv_ppt_series(
  mode = c("dark", "light"),
  colours = NULL,
  shapes = NULL,
  name = NULL,
  ...,
  colors = colours
)

Arguments

mode: Slide background the plot will sit on. "dark" pairs with theme_hv_ppt_dark(), "light" with theme_hv_ppt_light().
colours: The same as colors: an alias kept for existing code. Give one or the other; both with different values is an error.
shapes: Numeric vector of ggplot2 point shapes, one per group in order. Default NULL uses solid glyphs first.
name: Title used by both scales, so a drawn legend merges into one. Default NULL draws no title. Unused while the legend is off.
...: Additional named arguments forwarded to the underlying theme_hv_ppt_*() call, e.g. base_size = 28 or legend.position = "top".
colors: Character vector of colors, one per group in order. Default NULL uses the Okabe-Ito ordering for mode.

Value

A list of ggplot2 components: a theme, a color scale and a shape scale. Add it to a ggplot object with +.

Details

The return value is a plain list, and ggplot2's + unrolls a list element by element, so it composes like a theme:

ppt <- hv_ppt_series()
p1  <- p1 + ppt
p2  <- p2 + ppt

A theme cannot do this job alone. ggplot2::theme() governs the non-data ink, the text, panel, grid and ticks, and nothing that draws from the data, so no theme element sets a series color. Nor can a layer be smuggled in through the theme's ..., which is forwarded to ggplot2::theme() and errors on anything that is not a theme element. Series color and shape live in the scales, and those are what this function adds alongside the theme.

Color and shape carry the same variable

Both scales map the grouping column, so each series is told apart twice. That redundancy is the point. A projector in a dark room flattens color differences that read cleanly on your monitor, and a black and white handout drops them entirely, but the shapes survive both. The two scales share name, so on the rare draft that does draw a legend, ggplot2 merges them into one instead of stacking two.

The default colors are the Okabe-Ito colorblind-safe palette, ordered for the background: high-luminance hues first on a dark slide, darker ones first on a light slide. These are not CORR brand colors. Pass colors when a deck calls for a specific set.

Six colors and six shapes are supplied, which covers a grouping variable of up to six levels. A discrete scale errors when it runs out of values, so pass longer vectors for a wider variable.

No legend, by house standard

Every theme_hv_*() sets legend.position = "none", and this decorator leaves that alone. CORR figures name the series where the series sits, on a slide, on a poster and in a manuscript alike, so the reader's eye never travels out to a key and back.

Annotation is drawn in the theme's ink, not in the color of the series it names: white on a dark slide, black on a light slide and in a manuscript. That is the ink the theme already gives the axis text and axis lines, so one ink for every label makes the annotation read as part of the figure's frame rather than as one more series.

plot(trends) +
  hv_ppt_series("dark") +
  ggplot2::annotate("text", x = 2015, y = 60, label = "Group I",
                    color = "white", size = 8)

The shape scale still earns its place with no legend drawn. Where two curves cross, the plotted summary points are what tells them apart.

Pass legend.position = "top" through ... when a working draft wants a quick key, or hand the finished plot to hv_legend_inside() to drop one into an empty corner of the panel.

Grouped plots only

The scales take effect on a plot that maps color to a grouping column, which means a constructor called with group_col. On an ungrouped plot they sit unused and only the theme applies. There is nothing to fix in that case; a single series needs no palette. To color the raw observations on an ungrouped plot, add your own layer after the decorator, for example + ggplot2::geom_point(color = "yellow").

Examples

dta <- sample_trends_data(n = 400, seed = 42)
trends <- hv_trends(dta, x_col = "year", y_col = "value",
                    group_col = "group")

# One decorator, added to every plot in the deck.
ppt <- hv_ppt_series(mode = "dark")
plot(trends) + ppt


# House style carries no legend, so name the series where it sits. The
# label takes the same ink as the axis: white on a dark slide, black on a
# light one.
plot(trends) + ppt +
  ggplot2::annotate("text", x = 2015, y = 60, label = "Group I",
                    color = "white", size = 8)


# A light template, larger type, and your own colors.
plot(trends) +
  hv_ppt_series(
    mode      = "light",
    colors    = c("#0072B2", "#D55E00", "#009E73", "#CC79A7"),
    base_size = 24
  )