Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from therepeat operator.

See also:field documentation.

Notes: 1) Dots (.) and brackets ([ and]) can be used to access nested objects (e.g.,"field": "foo.bar" and"field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use\\ to escape dots and brackets (e.g.,"a\\.b" and"a\\[0\\]"). See more details about escaping in thefield documentation. 2)field is not required ifaggregate iscount.

The type of measurement ("quantitative","temporal","ordinal", or"nominal") for the encoded field or constant value (datum). It can also be a"geojson" type for encoding‘geoshape’.

Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specifiedaggregate (exceptargmin andargmax),bin, scale type, customsort order, nortimeUnit or (2) if you wish to use an ordinal scale for a field withbin ortimeUnit.

Default value:

1) For a datafield,"nominal" is the default data type unless the field encoding hasaggregate,channel,bin, scale type,sort, ortimeUnit that satisfies the following criteria:

• "quantitative" is the default type if (1) the encoded field containsbin oraggregate except"argmin" and"argmax", (2) the encoding channel islatitude orlongitude channel or (3) if the specified scale type isa quantitative scale.
• "temporal" is the default type if (1) the encoded field containstimeUnit or (2) the specified scale type is a time or utc scale
• "ordinal" is the default type if (1) the encoded field contains acustomsort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel isorder.

2) For a constant value in data domain (datum):

• "quantitative" if the datum is a number
• "nominal" if the datum is a string
• "temporal" if the datum isa date time object

Note:

• Datatype describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data.
• Data values for a temporal field can be either a date-time string (e.g.,"2015-03-07 12:32:17","17:01","2015-03-16"."2015") or a timestamp number (e.g.,1552199579097).
• When using withbin, thetype property can be either"quantitative" (for using a linear bin scale) or"ordinal" (for using an ordinal bin scale).
• When using withtimeUnit, thetype property can be either"temporal" (default, for using a temporal scale) or"ordinal" (for using an ordinal scale).
• When using withaggregate, thetype property refers to the post-aggregation data type. For example, we can calculate countdistinct of a categorical field"cat" using{"aggregate": "distinct", "field": "cat"}. The"type" of the aggregate output is"quantitative".
• Secondary channels (e.g.,x2,y2,xError,yError) do not havetype as they must have exactly the same type as their primary channels (e.g.,x,y).

See also:type documentation.

A flag for binning aquantitative field,an object defining binning parameters, or indicating that the data forx ory channel are binned before they are imported into Vega-Lite ("binned").

• Iftrue, defaultbinning parameters will be applied.

• If"binned", this indicates that the data for thex (ory) channel are already binned. You can map the bin-start field tox (ory) and the bin-end field tox2 (ory2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’stickMinStep property.

Default value:false

See also:bin documentation.

Time unit (e.g.,year,yearmonth,month,hours) for a temporal field. ora temporal field that gets casted as ordinal.

Default value:undefined (None)

See also:timeUnit documentation.

Aggregation function for the field (e.g.,"mean","sum","median","min","max","count").

Default value:undefined (None)

See also:aggregate documentation.

A title for the field. Ifnull, the title will be removed.

Default value: derived from the field’s name and transformation function (aggregate,bin andtimeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g.,"Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g.,"Profit (binned)","Transaction Date (year-month)"). Otherwise, the title is simply the field name.

Notes:

1) You can customize the default field title format by providing thefieldTitle property in theconfig orfieldTitle function via thecompile function’s options.

2) If both field definition’stitle and axis, header, or legendtitle are defined, axis/header/legend title will be used.

A constant value in data domain.

X coordinates of the marks, or width of horizontal"bar" and"area" without specifiedx2 orwidth.

Thevalue of this channel can be a number or a string"width" for the width of the plot.

Y coordinates of the marks, or height of vertical"bar" and"area" without specifiedy2 orheight.

Thevalue of this channel can be a number or a string"height" for the height of the plot.

X2 coordinates for ranged"area","bar","rect", and"rule".

Thevalue of this channel can be a number or a string"width" for the width of the plot.

Y2 coordinates for ranged"area","bar","rect", and"rule".

Thevalue of this channel can be a number or a string"height" for the height of the plot.

An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels.

Ifnull, the scale will bedisabled and the data value will be directly encoded.

Default value: If undefined, defaultscale properties are applied.

See also:scale documentation.

An object defining properties of axis’s gridlines, ticks and labels. Ifnull, the axis for the encoding channel will be removed.

Default value: If undefined, defaultaxis properties are applied.

See also:axis documentation.

Sort order for the encoded field.

For continuous fields (quantitative or temporal),sort can be either"ascending" or"descending".

For discrete fields,sort can be one of the following:

• "ascending" or"descending" – for sorting by the values’ natural order in JavaScript.
• A string indicating an encoding channel name to sort by (e.g.,"x" or"y") with an optional minus prefix for descending sort (e.g.,"-x" to sort by x-field, descending). This channel string is short-form ofa sort-by-encoding definition. For example,"sort": "-x" is equivalent to"sort": {"encoding": "x", "order": "descending"}.
• A sort field definition for sorting by another field.
• An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can bedate-time definition objects. In addition, for time units"month" and"day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g.,"Mon","Tue").
• null indicating no sort.

Default value:"ascending"

Note:null and sorting by another channel is not supported forrow andcolumn.

See also:sort documentation.

An object defining the properties of the Impute Operation to be applied. The field value of the other positional channel is taken askey of theImpute Operation. The field of thecolor channel if specified is used asgroupby of theImpute Operation.

See also:impute documentation.

Type of stacking offset if the field should be stacked.stack is only applicable forx,y,theta, andradius channels with continuous domains. For example,stack ofy can be used to customize stacking for a vertical bar chart.

stack can be one of the following values:

• "zero" ortrue: stacking with baseline offset at zero value of the scale (for creating typical stackedbar andarea chart).
• "normalize" - stacking with normalized domain (for creatingnormalized stacked bar and area charts and pie chartswith percentage tooltip).
  -"center" - stacking with center baseline (forstreamgraph).
• null orfalse - No-stacking. This will produce layeredbar and area chart.

Default value:zero for plots with all of the following conditions are true: (1) the mark isbar,area, orarc; (2) the stacked measure channel (x or y) has a linear scale; (3) At least one of non-position channels mapped to an unaggregated field that is different from x and y. Otherwise,null by default.

See also:stack documentation.

An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels.

Ifnull, the scale will bedisabled and the data value will be directly encoded.

Default value: If undefined, defaultscale properties are applied.

See also:scale documentation.

Sort order for the encoded field.

For continuous fields (quantitative or temporal),sort can be either"ascending" or"descending".

For discrete fields,sort can be one of the following:

• "ascending" or"descending" – for sorting by the values’ natural order in JavaScript.
• A string indicating an encoding channel name to sort by (e.g.,"x" or"y") with an optional minus prefix for descending sort (e.g.,"-x" to sort by x-field, descending). This channel string is short-form ofa sort-by-encoding definition. For example,"sort": "-x" is equivalent to"sort": {"encoding": "x", "order": "descending"}.
• A sort field definition for sorting by another field.
• An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can bedate-time definition objects. In addition, for time units"month" and"day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g.,"Mon","Tue").
• null indicating no sort.

Default value:"ascending"

Note:null and sorting by another channel is not supported forrow andcolumn.

See also:sort documentation.

• For arc marks, the arc length in radians if theta2 is not specified, otherwise the start arc angle. (A value of 0 indicates up or “north”, increasing values proceed clockwise.)

• For text marks, polar coordinate angle in radians.

The outer radius in pixels of arc marks.

The end angle of arc marks in radians. A value of 0 indicates up or “north”, increasing values proceed clockwise.

The inner radius in pixels of arc marks.

Longitude position of geographically projected marks.

Latitude position of geographically projected marks.

Longitude-2 position for geographically projected ranged"area","bar","rect", and"rule".

Latitude-2 position for geographically projected ranged"area","bar","rect", and"rule".

Rotation angle of point and text marks.

Color of the marks – either fill or stroke color based on thefilled property of mark definition. By default,color represents fill color for"area","bar","tick","text","trail","circle", and"square" / stroke color for"line" and"point".

Default value: If undefined, the default color depends onmark config’scolor property.

Note: 1) For fine-grained control over both fill and stroke colors of the marks, please use thefill andstroke channels. Thefill orstroke encodings have higher precedence thancolor, thus may override thecolor encoding if conflicting encodings are specified. 2) See the scale documentation for more information about customizingcolor scheme.

Fill color of the marks.Default value: If undefined, the default color depends onmark config’scolor property.

Note: Thefill encoding has higher precedence thancolor, thus may override thecolor encoding if conflicting encodings are specified.

Stroke color of the marks.Default value: If undefined, the default color depends onmark config’scolor property.

Note: Thestroke encoding has higher precedence thancolor, thus may override thecolor encoding if conflicting encodings are specified.

Opacity of the marks.

Default value: If undefined, the default opacity depends onmark config’sopacity property.

Fill opacity of the marks.

Default value: If undefined, the default opacity depends onmark config’sfillOpacity property.

Stroke opacity of the marks.

Default value: If undefined, the default opacity depends onmark config’sstrokeOpacity property.

Shape of the mark.

1. Forpoint marks the supported values include: - plotting shapes:"circle","square","cross","diamond","triangle-up","triangle-down","triangle-right", or"triangle-left". - the line symbol"stroke" - centered directional shapes"arrow","wedge", or"triangle" - a customSVG path string (For correct sizing, custom shape paths should be defined within a square bounding box with coordinates ranging from -1 to 1 along both the x and y dimensions.)

2. Forgeoshape marks it should be a field definition of the geojson data

Default value: If undefined, the default shape depends onmark config’sshape property. ("circle" if unset.)

Size of the mark.

• For"point","square" and"circle", – the symbol size, or pixel area of the mark.
• For"bar" and"tick" – the bar and tick’s size.
• For"text" – the text’s font size.
• Size is unsupported for"line","area", and"rect". (Use"trail" instead of line with varying size)

Stroke dash of the marks.

Default value:[1,0] (No dash).

Stroke width of the marks.

Default value: If undefined, the default stroke width depends onmark config’sstrokeWidth property.

An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels.

Ifnull, the scale will bedisabled and the data value will be directly encoded.

Default value: If undefined, defaultscale properties are applied.

See also:scale documentation.

An object defining properties of the legend. Ifnull, the legend for the encoding channel will be removed.

Default value: If undefined, defaultlegend properties are applied.

See also:legend documentation.

One or more value definition(s) witha parameter or a test predicate.

Note: A field definition’scondition property can only containconditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.

A field definition or one or more value definition(s) with a parameter predicate.

Text of thetext mark.

The tooltip text to show upon mouse hover. Specifyingtooltip encoding overridesthetooltip property in the mark definition.

See thetooltip documentation for a detailed discussion about tooltip in Vega-Lite.

The text format specifier for formatting number and date/time in labels of guides (axes, legends, headers) and text marks.

If the format type is"number" (e.g., for quantitative fields), this is a D3’snumber format pattern string.

If the format type is"time" (e.g., for temporal fields), this is either: a) D3’stime format pattern if you desire to set a static time format.

b)dynamic time format specifier object if you desire to set a dynamic time format that uses different formats depending on the granularity of the input date (e.g., if the date lies on a year, month, date, hour, etc. boundary).

When used with acustomformatType, this value will be passed asformat alongsidedatum.value to the registered function.

Default value: Derived fromnumberFormat config for number format and fromtimeFormat config for time format.

The format type for labels. One of"number","time", or aregistered custom format type.

Default value:

• "time" for temporal fields and ordinal and nominal fields withtimeUnit.
• "number" for quantitative fields as well as ordinal and nominal fields withouttimeUnit.

One or more value definition(s) witha parameter or a test predicate.

Note: A field definition’scondition property can only containconditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.

A field definition or one or more value definition(s) with a parameter predicate.

A URL to load upon mouse click.

A field definition or one or more value definition(s) with a parameter predicate.

A text description of this mark for ARIA accessibility (SVG output only). For SVG output the"aria-label" attribute will be set to this description.

The text format specifier for formatting number and date/time in labels of guides (axes, legends, headers) and text marks.

If the format type is"number" (e.g., for quantitative fields), this is a D3’snumber format pattern string.

If the format type is"time" (e.g., for temporal fields), this is either: a) D3’stime format pattern if you desire to set a static time format.

b)dynamic time format specifier object if you desire to set a dynamic time format that uses different formats depending on the granularity of the input date (e.g., if the date lies on a year, month, date, hour, etc. boundary).

When used with acustomformatType, this value will be passed asformat alongsidedatum.value to the registered function.

Default value: Derived fromnumberFormat config for number format and fromtimeFormat config for time format.

The format type for labels. One of"number","time", or aregistered custom format type.

Default value:

• "time" for temporal fields and ordinal and nominal fields withtimeUnit.
• "number" for quantitative fields as well as ordinal and nominal fields withouttimeUnit.

One or more value definition(s) witha parameter or a test predicate.

Note: A field definition’scondition property can only containconditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.

A field definition or one or more value definition(s) with a parameter predicate.

Additional levels of detail for grouping data in aggregate views and in line, trail, and area marks without mapping data to a specific visual channel.

A data field to use as a unique key for data binding. When a visualization’s data is updated, the key value will be used to match data elements to existing mark instances. Use a key channel to enable object constancy for transitions over dynamic data.

Order of the marks.

• For stacked marks, thisorder channel encodesstack order.
• For line and trail marks, thisorder channel encodes order of data points in the lines. This can be useful for creatinga connected scatterplot. Settingorder to{"value": null} makes the line marks use the original order in the data sources.
• Otherwise, thisorder channel encodes layer order of the marks.

Note: In aggregate plots,order field should beaggregated to avoid creating additional aggregation grouping.

The sort order. One of"ascending" (default) or"descending".

One or more value definition(s) witha parameter or a test predicate.

Note: A field definition’scondition property can only containconditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.

A field definition for the (flexible) facet of trellis plots.

If eitherrow orcolumn is specified, this channel will be ignored.

A field definition for the vertical facet of trellis plots.

A field definition for the horizontal facet of trellis plots.