Scale
Edit this pageScales are functions that transform a domain of data values (numbers, dates, strings, etc.) to a range of visual values (pixels, colors, sizes). Internally, VegaLite uses Vega scales, which are derived from the d3scale library. For more background about scales, please see “Introducing d3scale” by Mike Bostock.
VegaLite automatically creates scales for fields that are mapped to position and mark property channels.
To customize the scale of a field, users can provide a scale
object as a part of the field definition to customize scale properties (e.g., type, domain, and range).
// Single View Specification
{
"data": ... ,
"mark": ... ,
"encoding": {
"x": {
"field": ...,
"type": ...,
"scale": { // scale
"type": ...,
...
},
...
},
"y": ...,
...
},
...
}
Besides the scale
property of each encoding channel, the toplevel configuration object (config
) also provides scale config (config: {scale: {...}}
) for setting default scale properties for all scales.
For more information about guides that visualize the scales, please see the axes and legends pages.
Documentation Overview
 Scale Types
 Scale Domains
 Scale Ranges
 Continuous Scales
 Discrete Scales
 Discretizing Scales
 Configuration
Scale Types
The type
property can be specified to customize the scale type.
Property  Type  Description 

type  String 
The type of scale. VegaLite supports the following categories of scale types: 1) Continuous Scales – mapping continuous domains to continuous output ranges ( 2) Discrete Scales – mapping discrete domains to discrete ( 3) Discretizing Scales – mapping continuous domains to discrete output ranges ( Default value: please see the scale type table. 
By default, VegaLite use the following scale types for the following data types and encoding channels:
Nominal / Ordinal  Quantitative  BinQuantitative^{1}  Temporal  

X, Y  Band / Point^{2}  Linear  Linear ^{3}  Time 
Size, Opacity  Point  Linear  BinLinear  Time 
Color  Ordinal  Sequential  BinOrdinal  Sequential 
Shape  Ordinal  N/A  N/A  N/A 
^{1} Quantitative fields with the bin
transform.
^{2} For positional (x and y) ordinal and ordinal fields, "point"
is the default scale type for all marks except
bar and rect marks, which use "band"
scales.
^{3} For static plots, both "linear"
and "binlinear"
work with binned fields on x and y. However, panning and zooming do not work with discretized scales such as "binlinear"
, thus we use "linear"
as the default scale type for binned fields on x and y.
Scale Domains
By default, a scale in VegaLite draws domain values directly from a channel’s encoded field. Users can specify the domain
property of a scale to customize its domain values. To sort the order of the domain of the encoded, the sort
property of a field definition can be specified.
Property  Type  Description 

domain  Number[]  String[]  Boolean[]  DateTime[]  String  SelectionDomain 
Customized domain values. For quantitative fields, For temporal fields, For ordinal and nominal fields, The 
Scale Ranges
The range of the scale represents the set of output visual values. VegaLite automatically determines the default range for each encoding channel using the following rules:
Channels  Default Range 

x 
The range is always [0, width] . Any directly specified range will be ignored. Range can be customized via the view’s width property or via range steps and paddings properties for band and point scales. 
y 
The range is always [0, height] . Any directly specified range will be ignored. Range can be customized via the view’s height property or via range steps and paddings properties for band and point scales. 
opacity 
Derived from the scale config’s min/maxOpacity . 
color 
Derived from the following named ranges based on the field’s type : • "category" for nominal fields. • "ordinal" for ordinal fields. • "heatmap" for quantitative and temporal fields with "rect" marks and "ramp' for other marks. See the color scheme section for examples. 
size 
Derived from the following named ranges based on the mark type: • min/maxBandSize for bar and tick. • min/maxStrokeWidth for line and rule. • min/maxSize for point, square, and circle • min/maxFontSize for text 
shape 
Derived from the predefined named range "symbol" . 
To customize range values, users can directly specify range
, or the special range properties: rangeStep
and padding
for band and point scales and scheme
for ordinal and sequential color scales.
Property  Type  Description 

range  Number[]  String[]  String 
The range of the scale. One of:
Notes: 1) For sequential, ordinal, and discretizing color scales, you can also specify a color 2) Any directly specified 
Color Schemes
Color schemes provide a set of named color palettes as a scale range for the color
channel. VegaLite (via Vega) provides a collection of perceptuallymotivated color schemes, many of which are drawn from the d3scale, d3scalechromatic, and ColorBrewer projects.
By default, VegaLite assigns different default color schemes based on the types of the encoded fields:

Nominal fields use the
"categorical"
predefined named range (the"category20"
scheme by default).

Ordinal fields use the
"ordinal"
predefined named color range (the"blues"
color scheme by default).

Quantitative and temporal fields use the predefined named color range
"heatmap"
(the"viridis"
scheme by default) for rect marks and"ramp"
(the"blues"
scheme by default) for other marks.
There are multiple ways to customize the scale range for the color encoding channel:
1) Set a custom scheme
.
Property  Type  Description 

scheme  String  SchemeParams 
A string indicating a color scheme name (e.g., Discrete color schemes may be used with discrete or discretizing scales. Continuous color schemes are intended for use with sequential scales. For the full list of supported scheme, please refer to the Vega Scheme reference. 
For example, the following plot use the "category20b"
scheme.
The scheme
property can also be a scheme parameter object, which contain the following properties:
Property  Type  Description 

name  String 
Required. A color scheme name for sequential/ordinal scales (e.g., For the full list of supported scheme, please refer to the Vega Scheme reference. 
extent  Number[] 
For sequential and diverging schemes only, determines the extent of the color range to use. For example 
2) Setting the range
property to an array of valid CSS color strings.
3) Change the default color schemes using the range config.
Continuous Scales
Continuous scales map a continuous domain (numbers or dates) to a continuous output range (pixel locations, sizes, colors). Supported continuous scale types for quantitative fields are "linear"
, "log"
, "pow"
, "sqrt"
, and "sequential"
. Meanwhile, supported continuous scale types for temporal fields are "time"
, "utc"
, and "sequential"
.
By default, VegaLite uses "linear"
scales for quantitative fields and uses "time"
scales for temporal fields for all encoding channels except for color
, which uses "sequential"
scales for both quantitative and temporal fields.
In addition to type
, domain
, and range
, continuous scales support the following properties:
Property  Type  Description 

clamp  Boolean 
If Default value: derived from the scale config’s 
interpolate  String  Object 
The interpolation method for range values. By default, a general interpolator for numbers, dates, strings and colors (in RGB space) is used. For color ranges, this property allows interpolation in alternative color spaces. Legal values include Note: Sequential scales do not support 
nice  Boolean  Number  String  Object 
Extending the domain so that it starts and ends on nice round values. This method typically modifies the scale’s domain, and may only extend the bounds to the nearest round value. Nicing is useful if the domain is computed from data and may be irregular. For example, for a domain of [0.201479…, 0.996679…], a nice domain might be [0.2, 1.0]. For quantitative scales such as linear, For temporal fields with time and utc scales, the Default value: 
padding  Number 
For continuous scales, expands the scale domain to accommodate the specified number of pixels on each of the scale range. The scale range must represent pixels for this parameter to function as intended. Padding adjustment is performed prior to all other adjustments, including the effects of the zero, nice, domainMin, and domainMax properties. For band scales, shortcut for setting For point scales, alias for Default value: For continuous scales, derived from the scale config’s 
round  Boolean 
If Default value: 
zero  Boolean 
If Default value: Note: Log, time, and utc scales do not support 
Linear Scales
Linear scales ("linear"
) are quantitative scales scales that preserve proportional differences. Each range value y can be expressed as a linear function of the domain value x: y = mx + b.
Power Scales
Power scales ("pow"
) are quantitative scales scales that apply an exponential transform to the input domain value before the output range value is computed. Each range value y can be expressed as a polynomial function of the domain value x: y = mx^k + b, where k is the exponent
value. Power scales also support negative domain values, in which case the input value and the resulting output value are multiplied by 1.
Property  Type  Description 

exponent  Number 
The exponent of the 
Square Root Scales
Square root ("sqrt"
) scales are a convenient shorthand for power scales with an exponent
of 0.5
, indicating a square root transform.
Logarithmic Scales
Log scales ("log"
) are quantitative scales in which a logarithmic transform is applied to the input domain value before the output range value is computed. Log scales are particularly useful for plotting data that varies over multiple orders of magnitude. The mapping to the range value y can be expressed as a logarithmic function of the domain value x: y = m log_{a}(x) + b, where a is the logarithmic base
.
As log(0) = ∞, a log scale domain must be strictlypositive or strictlynegative; the domain must not include or cross zero. A log scale with a positive domain has a welldefined behavior for positive values, and a log scale with a negative domain has a welldefined behavior for negative values. (For a negative domain, input and output values are implicitly multiplied by 1.) The behavior of the scale is undefined if you run a negative value through a log scale with a positive domain or vice versa.
Property  Type  Description 

base  Number 
The logarithm base of the 
Example: The following plot has a logarithmic yscale.
Time and UTC Scales
Time and UTC scales ("time"
and "utc"
) are continuous scales with a temporal domain: values in the input domain are assumed to be Date objects or timestamps. Time scales use the current local timezone setting. UTC scales instead use Coordinated Universal Time.
Sequential Scales
Sequential scales ("sequential"
) are similar to linear scales, but use a fixed interpolator to determine the output range. By default, Vegalite uses sequential scales to encode continuous (quantitative and temporal) fields with color
s.
To customize the range of a sequential scale, either a range
array listing colors or a color scheme
can be specified.
Piecewise Scales
We can use any types of continuous scales ("linear"
, "pow"
, "sqrt"
, "log"
, "time"
, "utc"
, "sequential"
) to create a diverging color graph by specifying a custom domain
with multiple elements.
If range
is specified, the number of elements in range
should match with the number of elements in domain
. Diverging color scheme
s are also useful as a range for a piecewise scale.
Example
Discrete Scales
Discrete scales map values from a discrete domain to a discrete or continuous range.
Ordinal Scales
Ordinal scales ("ordinal"
) have a discrete domain and range. These scales function as a “lookup table” from a domain value to a range value.
By default, VegaLite automatically creates ordinal scales for color
and shape
channels. For example, the following plot implicitly has two ordinal scales, which map the values of the field "Origin"
to a set of color
s and a set of shape
s.
The range
of an ordinal scale can be an array of desired output values, which are directly mapped to elements in the domain
. Both domain
and range
array can be reordered to specify the order and mapping between the domain and the output range. For ordinal color scales, a custom scheme
can be set as well.
Band and Point Scales
Band and point scales accept a discrete domain similar to ordinal scales, but map this domain to a continuous, numeric output range such as pixels.
Band scales ("band"
) compute the discrete output values by dividing the continuous range into uniform bands. Band scales are typically used for bar charts with an ordinal or categorical dimension.
In addition to a standard numerical range value (such as [0, 500]
), band scales can be given a fixed step size for each band. The actual range is then determined by both the step size and the cardinality (element count) of the input domain.
This image from the d3scale documentation illustrates how a band scale works:
Point scales ("point"
) are a variant of band scales where the internal band width is fixed to zero. Point scales are typically used for scatterplots with an ordinal or categorical dimension. Similar to band scales, point scale range values may be specified using either a numerical extent ([0, 500]
) or a step size ({"step": 20}
).
This image from the d3scale documentation illustrates how a point scale works:
By default, VegaLite uses band scales for nominal and ordinal fields on position channels (x
and y
) of bar or rect marks.
For x
and y
of other marks and size
and opacity
, VegaLite uses point scales by default.
For example, the following bar chart has uses a band scale for its xposition.
To customize the range of band and point scales, users can provide the following properties:
Property  Type  Description 

padding  Number 
For continuous scales, expands the scale domain to accommodate the specified number of pixels on each of the scale range. The scale range must represent pixels for this parameter to function as intended. Padding adjustment is performed prior to all other adjustments, including the effects of the zero, nice, domainMin, and domainMax properties. For band scales, shortcut for setting For point scales, alias for Default value: For continuous scales, derived from the scale config’s 
paddingInner  Number 
The inner padding (spacing) within each band step of band scales, as a fraction of the step size. This value must lie in the range [0,1]. For point scale, this property is invalid as point scales do not have internal band widths (only step sizes between bands). Default value: derived from the scale config’s 
paddingOuter  Number 
The outer padding (spacing) at the ends of the range of band and point scales, as a fraction of the step size. This value must lie in the range [0,1]. Default value: derived from the scale config’s 
rangeStep  Number  Null 
The distance between the starts of adjacent bands or points in band and point scales. If Default value: derived the scale config’s Warning: If 
round  Boolean 
If Default value: 
For example, we can set the rangeStep
property to make the bands of the bars smaller.
Discretizing Scales
Discretizing scales break up a continuous domain into discrete segments, and then map values in each segment to a range value.
BinLinear Scales
Binned linear scales ("binlinear"
) are a special type of linear scale for use with binned fields to correctly create legend labels.
VegaLite always uses binned linear scales with binned quantitative fields on size and opacity channels.
For example, the following plot has a binned field on the size
channel.
BinOrdinal Scales
Binned ordinal scales ("binordinal"
) are a special type of ordinal scale for use with binned fields to correctly create legend labels.
VegaLite always uses binned ordinal scales with binned quantitative fields on the color channel.
For example, the following plot has a binned field on the color
channel.
Similar to ordinal color scales, a custom range
or scheme
can be specified for binned ordinal scales.
Configuration
// Toplevel View Specification
{
...
"config": {
"scale": {
... // Scale Config
},
"range": {
... // Scale Range Config
},
...
}
...
}
Scale Config
To provide themes for all scales, the scale config (config: {scale: {...}}
) can contain the following properties:
Property  Type  Description 

bandPaddingInner  Number 
Default inner padding for Default value: 
bandPaddingOuter  Number 
Default outer padding for 
clamp  Boolean 
If true, values that exceed the data domain are clamped to either the minimum or maximum range value 
maxBandSize  Number 
The default max value for mapping quantitative fields to bar’s size/bandSize. If undefined (default), we will use the scale’s 
minBandSize  Number 
The default min value for mapping quantitative fields to bar and tick’s size/bandSize scale with zero=false. Default value: 
maxFontSize  Number 
The default max value for mapping quantitative fields to text’s size/fontSize. Default value: 
minFontSize  Number 
The default min value for mapping quantitative fields to tick’s size/fontSize scale with zero=false Default value: 
maxOpacity  Number 
Default max opacity for mapping a field to opacity. Default value: 
minOpacity  Number 
Default minimum opacity for mapping a field to opacity. Default value: 
maxSize  Number 
Default max value for point size scale. 
minSize  Number 
Default minimum value for point size scale with zero=false. Default value: 
maxStrokeWidth  Number 
Default max strokeWidth for strokeWidth (or rule/line’s size) scale. Default value: 
minStrokeWidth  Number 
Default minimum strokeWidth for strokeWidth (or rule/line’s size) scale with zero=false. Default value: 
pointPadding  Number 
Default outer padding for Default value: 
rangeStep  Number  Null 
Default range step for band and point scales of (1) the Default value: 
round  Boolean 
If true, rounds numeric output values to integers.
This can be helpful for snapping to the pixel grid.
(Only available for 
textXRangeStep  Number 
Default range step for Default value: 
useUnaggregatedDomain  Boolean 
Use the source data range before aggregation as scale domain instead of aggregated data for aggregate axis. This is equivalent to setting This property only works with aggregate functions that produce values within the raw data domain ( Default value: 
Range Config
The scale range configuration (config: {range: {...}}
) defines keyvalue mapping for named scale ranges: the keys represent the range names, while the values define valid range
or, for named color ranges, Vega scheme definitions.
By default, VegaLite (via Vega) includes the following predefined named ranges:
Property  Type  Description 

category  String[]  VgScheme 
Default range for nominal (categorical) fields. 
diverging  String[]  VgScheme 
Default range for diverging quantitative fields. 
heatmap  String[]  VgScheme 
Default range for quantitative heatmaps. 
ordinal  String[]  VgScheme 
Default range for ordinal fields. 
ramp  String[]  VgScheme 
Default range for quantitative and temporal fields. 
symbol  String[] 
Default range palette for the 
See this file for the default values of named ranges.