Struct ScaleDiscrete 

pub struct ScaleDiscrete { /* private fields */ }

Discrete scale: maps categorical values to evenly-spaced positions.

Implementations

impl ScaleDiscrete

pub fn new() -> Self

pub fn for_aesthetic(self, aes: Aesthetic) -> Self

pub fn with_name(self, name: &str) -> Self

pub fn with_labels(self, labels: Vec<String>) -> Self

Set custom display labels for each level. Must match the number of levels.

pub fn with_limits(self, limits: Vec<&str>) -> Self

Set level order and filter. Only these levels are shown, in this order. Data values not in limits are mapped to the middle (0.5).

Trait Implementations

impl Clone for ScaleDiscrete

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 ScaleDiscrete

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

Formats the value using the given formatter.

impl Default for ScaleDiscrete

fn default() -> Self

Returns the “default value” for a type.

impl Scale for ScaleDiscrete

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

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

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 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 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 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.