vega-scale
Scales and color schemes for visual encoding.
This module provides scale and scheme methods for
managing scale mappings and color schemes. By default, the scale and
scheme registries include all scale types and color schemes provided
by the D3 4.0 d3-scale and
d3-scale-chromatic modules.
This module also provides augmented implementations of 'band'
, 'point'
,
and 'sequential'
scales in order to provide improved layout and
inversion support for band/point scales, and multi-domain and color range
array support for sequential scales.
API Reference
#
vega.scale(type[, scale])
<>
Registry function for adding and accessing scale constructor functions.
The type argument is a String indicating the name of the scale type.
If the scale argument is not specified, this method returns the matching
scale constructor in the registry, or null
if not found.
If the scale argument is provided, it must be a scale constructor function
to add to the registry under the given type name.
By default, the scale registry includes entries for all scale types provided
by D3 4.0's d3-scale module. Scales created
using the constructor returned by this method have an additional type
property indicating the scale type. All scales supporting either an invert
or invertExtent
method are augmented with an additional invertRange
function that returns an array of corresponding domain values for a given
interval in the scale's output range.
var linear = vega.scale('linear');
var scale = linear().domain([0, 10]).range([0, 100]);
scale.type;
scale.invertRange([0, 100]);
var ordinal = vega.scale('ordinal');
var scale1 = ordinal().domain(['a', 'b', 'c']).range([0, 1, 2]);
scale1.type;
var scale2 = ordinal().range(vega.scheme('category20'));
var seq = vega.scale('sequential');
var scale1 = seq().interpolator(vega.scheme('plasma'));
scale1.type;
#
vega.scheme(name[, scheme])
<>
Registry function for adding and accessing color schemes.
The name argument is a String indicating the name of the color scheme.
If the scheme argument is not specified, this method returns the matching
scheme value in the registry, or null
if not found.
If the scheme argument is provided, it must be a valid color array or
interpolator
to add to the registry under the given name.
By default, the scheme registry includes entries for all scheme types
provided by D3 4.0's d3-scale and
d3-scale-chromatic module.
Valid schemes are either arrays of color values (e.g., applicable to
'ordinal'
scales) or
interpolator
functions (e.g., applicable to 'sequential'
scales.)
#
vega.interpolate(name[, gamma])
<>
Returns the D3 interpolator factory with the given name and optional
gamma. All interpolator types provided by the
d3-interpolate module are supported.
However, Vega uses hyphenated rather than camelCase names.
var rgbBasis = vega.interpolate('rgb-basis');
var rgbGamma = vega.interpolate('rgb', 2.2);
#
vega.interpolateRange(interpolator, range])
<>
Given a D3 interpolator instance, return a new interpolator with a modified
interpolation range. The range argument should be a two element array
whose entries lie in the range [0, 1]. This method is convenient for
transforming the range of values over which interpolation is performed.
var number = d3.interpolateNumber(0, 10);
number(0);
number(0.5);
number(1);
var range = vega.interpolateRange(number, [0.2, 0.8]);
range(0);
range(0.5);
range(1);