Struct ScaleColorDiscrete 

pub struct ScaleColorDiscrete { /* private fields */ }

Discrete color scale — maps categories to distinct colors.

Implementations

impl ScaleColorDiscrete

pub fn new(aesthetic: Aesthetic) -> Self

pub fn with_generated(self, p: GeneratedPalette) -> Self

Colours computed for the number of levels (ggplot2’s hue_pal() / viridis_pal()), e.g. GeneratedPalette::Hue(HuePalette::default()) — exactly ggplot2’s default colours for any number of groups.

pub fn sorted(self) -> Self

Order levels lexicographically (instead of first appearance) so a given level always gets the same palette colour and legend position across charts, whatever order the data arrives in — no need to pre-sort levels and repeat a manual palette per chart.

pub fn with_palette(self, colors: Vec<RGBAColor>) -> Self

pub fn with_named_palette(self, name: &PaletteName) -> Self

pub fn with_levels(self, levels: Vec<String>) -> Self

Pre-seed the factor levels (order), so each level keeps a fixed palette color regardless of which levels are present in the data — e.g. for a legend whose series can be toggled without the colors reshuffling.

pub fn color_for_index(&self, idx: usize) -> RGBAColor

Get color for a given level index.

pub fn color_for_value(&self, value: &Value) -> RGBAColor

Get color for a value.

pub fn levels(&self) -> &[String]

Trait Implementations

impl Clone for ScaleColorDiscrete

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ScaleColorDiscrete

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Scale for ScaleColorDiscrete

fn aesthetic(&self) -> Aesthetic

Which aesthetic this scale is for.

fn train(&mut self, values: &[Value])

Incorporate data values to determine domain.

fn map(&self, value: &Value) -> f64

Map a data value to a [0, 1] normalized position (position scales) or to a concrete visual value index (color/size scales).

fn breaks(&self) -> Vec<(f64, String)>

Generate break positions and labels for axis/legend.

fn name(&self) -> &str

Human-readable name (axis title).

fn set_name(&mut self, name: &str)

Set the scale name.

fn is_discrete(&self) -> bool

Whether this is a discrete scale.

fn map_to_color(&self, value: &Value) -> Option<(u8, u8, u8)>

Map a data value to an RGB color. Default returns None.

fn clone_box(&self) -> Box<dyn Scale>

Clone this scale into a boxed trait object.

fn reset_training(&mut self)

Reset training state so the scale can be retrained on new data.

fn transform(&self, value: &Value) -> Value

Apply transformation to raw data (e.g., log10).

fn na_fill_pattern(&self) -> Option<FillPattern>

A pattern fill for a value this scale draws with its flat na colour (Value::Na, or whatever else a scale treats that way) — ScaleFillBinned::na_pattern (#206) is the only implementor so far. Default None: the flat colour from map_to_color wins, unchanged. A geom that draws filled areas (geom_sf/geom_polygon/geom_rect/ geom_tile) checks this before falling back to map_to_color’s na-colour branch, and the legend’s “no data” key checks it too.

fn is_na_break(&self, _label: &str) -> bool

Whether label (a breaks label) is this scale’s “no data” legend key, so the legend draws that one key with na_fill_pattern instead of its ordinary flat swatch colour. Default false (no scale without an na key needs this). ScaleFillBinned overrides it.

fn breaks_for_layout(&self) -> Vec<(f64, String)>

Labels to measure when sizing a legend’s auto-wrap layout (guide::legend::plan_legend’s per-key pitch sums) — never what’s actually drawn, which stays breaks. Default: identical to breaks(), so every scale but one is unaffected. ScaleFillBinned::count_reserve (sipemu/ggplot-rs#271) overrides this: a legend whose key labels carry a trained count ("10–50 (12)") measures as if every count had the widest expected digit width, so the legend’s row count — and so the panel — stays stable across renders whose counts differ only in digit width (an animated map’s frames, sharing one GGPlot built once per frame with the same breaks/colours).

fn bin_edge_labels(&self) -> Option<Vec<String>>

A binned scale’s labels for its bin edges — one more than its breaks() (one per bin) — which guide_bins() (#409) draws at the boundaries between keys. None (the default) for every other scale.

fn map_to_shape(&self, _value: &Value) -> Option<PointShape>

Map a data value to a point shape. Default returns None.

fn map_to_linetype(&self, _value: &Value) -> Option<Linetype>

Map a data value to a linetype. Default returns None.

fn map_to_size(&self, _value: &Value) -> Option<f64>

Map a data value to a point size (radius in pixels). Default returns None.

fn map_to_alpha(&self, _value: &Value) -> Option<f64>

Map a data value to an alpha (opacity) value. Default returns None.

fn sec_axis(&self) -> Option<&SecAxis>

Get the secondary axis specification, if any.

fn set_default_locale(&mut self, _locale: &Locale)

Adopt a plot-level default Locale for the default break labels (number marks, month names, date formats), unless the scale already has its own. Called by the plot builder when GGPlot::locale is set. Default: ignored (scales without numeric/date labels).

fn locale(&self) -> Option<&Locale>

The locale this scale’s default labels are rendered with, if any.

fn format_value(&self, _value: &Value) -> Option<String>

Format a single raw (pre-scale-transform) data value for a per-mark attribute (data-fvalue/data-fx, B2-4) or a tooltip template placeholder — e.g. a de-DE currency string, or a datetime x’s ISO/locale date, independent of how the axis itself abbreviates its break labels. None for a missing/non-finite value, or a scale with nothing meaningful to format (default: every scale except continuous position/size/linewidth and datetime/colour-continuous, which override this).

fn set_limits(&mut self, _min: f64, _max: f64)

Override the trained domain limits (used by coord_cartesian zoom).

fn filter_limits(&self) -> Option<(f64, f64)>

Return OOB filter limits if this scale was created with explicit limits (e.g., via xlim/ylim). Data outside these limits should be removed before stats.

fn domain(&self) -> Option<(f64, f64)>

Return the trained data domain (min, max) for continuous scales. Used by the colorbar legend to pass data-space values to map_to_color().

fn expanded_domain(&self) -> Option<(f64, f64)>

The data values at the panel edges (normalized 0 and 1) for a trained continuous position scale — the limits after expansion, in the scale’s transformed space. None for discrete / untrained / non-position scales.

fn axis_position_opposite(&self) -> bool

Whether this axis is drawn on the opposite side (x → top, y → right).

fn set_expand(&mut self, _mult: f64, _add: f64)

Set the expansion multiplier/additive constant (R’s expand = c(mult, add)), applied symmetrically to both ends. Used by CoordSf::train_scales (expand(false) passes (0.0, 0.0)) to pin an explicit xlim/ylim to the panel exactly. Default: no-op (discrete / non-position scales have no expansion to set).

fn clear_expand(&mut self, _lower: bool, _upper: bool)

Drop the expansion at the lower and / or upper end (a coord’s expand = FALSE for one side, #411). Default: no-op.

fn bin_positions(&mut self, _values: &[Value]) -> Option<Vec<Value>>

A binned position scale (scale_x_binned, #408) replaces each value with its bin’s midpoint before the stat runs; None (the default) leaves positions alone.

fn log_ticks(&self) -> Vec<(f64, u8)>

guide_axis_logticks() (#409): (position, kind) of the log10 ticks to draw on this axis — kind 0 at each decade (long), 1 at the 5s (mid), 2 at the other integers (short). Empty by default.

fn set_log_ticks(&mut self, _on: bool)

Switch log_ticks on or off. Default: no-op.

fn map_fraction_to_size(&self, _fraction: f64) -> Option<f64>

Map an already-computed [0, 1] scale fraction (as returned alongside each label by breaks) directly to an output size, bypassing the round trip through map — a discrete-style legend key only has the break’s rendered label, not its original data value, so a continuous scale can’t recover the fraction by re-mapping the label text. Default: None.

fn map_fraction_to_alpha(&self, _fraction: f64) -> Option<f64>

Map an already-computed [0, 1] scale fraction directly to an output alpha (opacity), the map_fraction_to_size equivalent for a continuous alpha scale’s discrete-style legend keys — see that method’s doc for why the fraction, not the label, is the input. Default: None.

fn validate(&self, _warnings: &mut Vec<String>)

Validate this scale’s configuration once training is complete (e.g. a transform undefined at the domain’s own limits) and push a human-readable warning for each problem found. Called once per scale after the final training pass, with the plot’s warnings sink — map/map_to_size run per mark at draw time and have no such access, so a scale-level problem must be reported here instead. Default: no-op.