Notable Additions:

• New transform (timeunit) and expression functions for handling date-time values.
• New transforms for more flexible 2D density estimation (kde2d), flexible isocontour generation (isocontour), and heatmap image rendering (heatmap).
• The image mark now supports dynamic image and smooth properties.
• The path mark has new rotation (angle) and scale properties (scaleX, scaleY).
• More flexible cornerRadius control for rect and group marks.

Deprecations:

• The contour transform is now deprecated and may be removed in a future major release. Instead, use the new, more expressive isocontour, kde2d, and heatmap transforms.

Changes from v5.7.3:

docs

• Add documentation for new features.
• Add density-heatmaps example.
• Add radar-chart example. (thanks @benib!)
• Update contour-plot example.
• Update population-pyramid example.
• Update volcano-countours example.

vega

• Add vega-time utilities.
• Add bar-time test specification.
• Add heatmap-image test specification.
• Add heatmap-sinusoids test specification.
• Add isocontour-airports test specification.
• Add isocontour-volcano test specification.
• Add scatter-plot-contours test specification.
• Add scatter-plot-heatmap test specification.
• Update test specifications to use top-level guide configuration properties.
• Update build scripts, adjust D3 externals for vega-core build.
• Fix dependencies to specific versions. (#2089)

vega-encode

• Add support for UTC formatType.
• Update time/utc scale formatting to use vega-time methods.
• Fix log scale tick filtering of explicit values. (#2138)

vega-functions

• Add timeUnitSpecifier expression function.
• Add timeOffset and utcOffset expression functions.
• Add timeSequence and utcSequence expression functions.
• Update timeFormat and utcFormat functions to use vega-time methods.
• Update dependencies.
• Fix day/month format bug. (#2096, thanks @jakevdp!)

vega-geo

• Add isocontour, heatmap, and kde2d transforms.
• Drop d3-contour dependency, use local implementation.
• Deprecate contour transform.

vega-loader

• Update dependencies.

vega-parser

• Add tickBand property for configuring band axis styles.
• Update tickOffset config for band-scale axes.
• Update dependencies.
• Fix symbol color configuration to consider values in parallel, not sequentially.

vega-regression

• Update dependencies.

vega-scale

• Update to use vega-time, drop internal time interval method.

vega-scenegraph

• Add angle, scaleX, and scaleY channels for path marks. (#2030, thanks @mathiastiberghien!)
• Add individual cornerRadius options for rect and group marks. (#1968, thanks @donghaoren!)
• Add image mark support for pre-loaded image property.
• Use cubic bezier curves for improved rectangle corners.
• Fix canvas renderer to always bound to visible view.
• Drop Image loaded flag, use built-in complete flag.

vega-schema

• Add UTC timeFormat and time format specifier to schema.
• Add angle, scaleX, and scaleY encoding channels to schema.
• Add cornerRadius encoding channels to schema.
• Add axis translate and tickBand properties to schema.
• Update axis, legend format schema.

vega-selections

• Add support for resolving multi selections. (thanks @arvind!)

vega-statistics

• Add exported bandwidthNRD method.
• Update dependencies.

vega-time

• Add new vega-time utility package.

vega-transforms

• Add TimeUnit transform.
• Add Bin transform interval parameter.
• Add Flatten transform index parameter. (#2114, thanks @Timmmm!)

vega-typings

• Add TimeUnit transform typings.
• Add Heatmap, Isocontour, and KDE2D transform typings.
• Add Bin transform interval parameter to typings.
• Add Flatten transform index parameter to typings.
• Add missing transform typings, refine parameter typings.
• Add UTC timeFormat and time format specifier typings.
• Add angle, scaleX, and scaleY encoding channels to typings.
• Add cornerRadius encoding channels to typings.
• Add axis translate and tickBand properties to typings.
• Update axis, legend format typings.

vega-view

• Update dependencies.

vega-view-transforms

• Add axis translate support to axis layout.
• Update dependencies.

vega-wordcloud

• Update dependencies.