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Split the combined (colour, shape) ggplotly legend into two clean legends

Source: R/plotly_split_legend.R
plotly_split_legend.Rd

plotly::ggplotly() flattens a ggplot with both a colour and a shape aesthetic into one trace per (colour, shape) combination and names the legend entries as tuples such as "(0,Sickerbox / Infiltration box)" – with two storage types and the 0..x / ">x" overflow palette that yields an unreadable legend. This helper post-processes the plotly object:

Usage

plotly_split_legend(
  pl,
  lang = c("de", "en"),
  colour_title = NULL,
  shape_title = NULL,
  add_shape_legend = TRUE
)

Arguments

pl

A plotly object as returned by plotly::ggplotly(p, tooltip = "text").

lang

Character. "de" or "en"; sets the default legend group titles.

colour_title

Character or NULL. Title of the colour legend group. Defaults to the language-specific "Number of overflow events".

shape_title

Character or NULL. Title of the storage-type legend group. Defaults to the language-specific "Storage type".

add_shape_legend

Logical. If TRUE (default), append the two legend-only storage-type entries.

Value

The modified plotly object.

Details

  • the real traces lose their legend entries; instead every overflow class gets one legend-only key drawn as a neutral circle in the class colour (a coloured square or triangle would wrongly suggest one specific storage type). The key shares its legend group with the real traces of that class, so clicking it toggles both storage types of the class together;

  • two legend-only keys (neutral grey filled square = infiltration box, filled triangle = gravel trench) are appended under their own storage-type group title, so the shape encoding is explained separately from the colours – set add_shape_legend = FALSE to skip them (e.g. for storage-type-faceted plots whose strips already label the panels). The keys are clickable: since a plotly trace can only carry one legend group (taken by the overflow class), a small JavaScript handler (via htmlwidgets::onRender()) toggles all traces drawn with that marker symbol, so each storage type can be shown or hidden individually; the key greys out to reflect the state;

  • the combined "colour,shape" legend-title annotation that ggplotly draws over the plot title is removed; group titles take its place and the legend moves to a vertical layout on the right, where the groups stack cleanly.

Traces whose name is not a "(colour,shape)" tuple (frontier lines, best markers, single-aesthetic plots) are left untouched, so the helper is safe to apply to any of the package's interactive plots.

Examples

if (FALSE) { # \dontrun{
p <- plot_cost_vs_evaporation(sim_results, param_grid, x = 5, lang = "de")
pl <- plotly::ggplotly(p, tooltip = "text")
pl <- plotly_split_legend(pl, lang = "de")
} # }