Give a plot's colour and shape their own legend sections

A ggplot mapping both colour and shape to discrete columns has two legends, but plotly::ggplotly() merges them into one with an entry per combination, named "(colour,shape)" under a "colour<br />shape" title. This draws them as ggplot2 does instead: one legend in two titled sections, an entry per colour level and one per shape level (in black, as ggplot2 draws shape keys). Clicking an entry hides or shows every trace of its level, and double-clicking one shows only its level (inst/src/legendSections.js).

Usage

split_color_shape_legend(
  fig,
  color.levels,
  shape.levels,
  color.title = NULL,
  shape.title = NULL,
  marker.size = 8
)

Arguments

fig

A built plotly figure.

color.levels, shape.levels

The colour and shape levels as plotted.

color.title, shape.title

The sections' titles. NULL takes each from the legend title ggplotly wrote.

marker.size

The size, in px, of the entries' markers.

Value

The figure, unchanged when no trace is drawn for a combination of a colour and a shape level.

Details

The point traces drawn for each combination are kept, out of the legend and tagged with their levels (in meta). A trace drawn for a colour alone, such as a yPlot's boxes ("(colour,1)", ggplot's placeholder shape for them), becomes its level's colour entry; a level without one gets a data-less legend-only trace, as does every shape level. Those are appended after the existing traces, so no trace's index (a selection's curve number) moves. Traces grouped under a colour level by name (the scatter plot's marginals) are hidden and shown with it.

See also

apply_legend_styling(), whose title fonts style the section titles.

Author

Jared Andrews

Examples

d <- transform(mtcars, am = factor(am), vs = factor(vs))
p <- ggplot2::ggplot(d, ggplot2::aes(wt, mpg, colour = am, shape = vs)) +
    ggplot2::geom_point()
fig <- plotly::plotly_build(plotly::ggplotly(p))
fig <- split_color_shape_legend(fig, levels(d$am), levels(d$vs))