Error Band

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// Single View Specification
{
  "data": ... ,
  "mark": "errorband",
  "encoding": ... ,
  ...
}

An error band summarizes an error range of quantitative values using a set of summary statistics, representing by area. Error band in Vega-Lite can either be used to aggregate raw data or directly visualize aggregated data.

To create an error band, set mark to "errorband".

Documentation Overview

Error Band Mark Properties

An error band’s mark definition can contain the following properties:

Property Type Description
type ErrorBand

Required. The mark type. This could a primitive mark type (one of "bar", "circle", "square", "tick", "line", "area", "point", "geoshape", "rule", and "text") or a composite mark type ("boxplot", "errorband", "errorbar").
extent String

The extent of the band. Available options include:

  • "ci": Extend the band to the confidence interval of the mean.
  • "stderr": The size of band are set to the value of standard error, extending from the mean.
  • "stdev": The size of band are set to the value of standard deviation, extending from the mean.
  • "iqr": Extend the band to the q1 and q3.

Default value: "stderr".
orient String

Orientation of the error band. This is normally automatically determined, but can be specified when the orientation is ambiguous and cannot be automatically determined.
color Color | Gradient | ExprRef

Default color.

Default value: ■ "#4682b4"

Note:

  • This property cannot be used in a style config.
  • The fill and stroke properties have higher precedence than color and will override color.
opacity Number

The opacity (value between [0,1]) of the mark.
interpolate String

The line interpolation method for the error band. One of the following:

  • "linear": piecewise linear segments, as in a polyline.
  • "linear-closed": close the linear segments to form a polygon.
  • "step": a piecewise constant function (a step function) consisting of alternating horizontal and vertical lines. The y-value changes at the midpoint of each pair of adjacent x-values.
  • "step-before": a piecewise constant function (a step function) consisting of alternating horizontal and vertical lines. The y-value changes before the x-value.
  • "step-after": a piecewise constant function (a step function) consisting of alternating horizontal and vertical lines. The y-value changes after the x-value.
  • "basis": a B-spline, with control point duplication on the ends.
  • "basis-open": an open B-spline; may not intersect the start or end.
  • "basis-closed": a closed B-spline, as in a loop.
  • "cardinal": a Cardinal spline, with control point duplication on the ends.
  • "cardinal-open": an open Cardinal spline; may not intersect the start or end, but will intersect other control points.
  • "cardinal-closed": a closed Cardinal spline, as in a loop.
  • "bundle": equivalent to basis, except the tension parameter is used to straighten the spline.
  • "monotone": cubic interpolation that preserves monotonicity in y.
tension Number

The tension parameter for the interpolation type of the error band.

Besides the properties listed above, band and borders can be used to specify the underlying mark properties for different parts of the error band as well.

Comparing the usage of Error Band to the usage of Error Bar

All the properties and usage of error band are identical to error bar’s, except the band and borders that replace the error bar’s rule and ticks.

Error Band

Error Bar

Using Error Band to Aggregate Raw Data

If the data is not aggregated yet, Vega-Lite will aggregate the data based on the extent properties in the mark definition as done in the error band showing confidence interval above. All other extent values are defined in Error Bar.

Using Error Band to Visualize Aggregated Data

  1. Data is aggregated with low and high values of the error band

If the data is already pre-aggregated with low and high values of the error band, you can directly specify x and x2 (or y and y2) to use error band as a ranged mark.

  1. Data is aggregated with center and error value(s)

If the data is already pre-aggregated with center and error values of the error band, you can use x/y, x/yError, and x/yError2 as defined in Error Bar

Dimension

Vega-Lite supports both 1D and 2D error bands:

{:#1d} A 1D error band shows the error range of a continuous field; it can be used to show the global error range of the whole plot.

{:#2d} A 2D error band shows the error range of a continuous field for each dimension value such as year.

The Parts of Error Band

Under the hood, the errorband mark is a composite mark that expands into a layered plot. For example, the basic 2D error band shown above is equivalent to:

We can customize different parts of the error band mark definition or config.

For example, we can add the error band’s borders and customize it by setting borders to true or adding a mark property to borders, such as strokeDash and opacity:

Color, and Opacity Encoding Channels

You can customize the color, size, and opacity of the band in the errorband by using the color, and opacity encoding channels, which applied to the whole errorband.

Here is an example of a errorband with the color encoding channel set to {"value": "black"}.

Tooltip Encoding Channels

You can add custom tooltips to error bands. The custom tooltip will override the default error band’s tooltips.

Mark Config

{
  "errorband": {
    "extent": ...,
    "band": ...,
    "borders": ...
  }
}

The errorband config object sets the default properties for errorband marks.

The error band config can contain all error band mark properties but currently not supporting color, opacity, and orient. Please see issue #3934.