d3-tricontour

This library computes contour polygons by applying meandering triangles to an array of points with arbitrary 2D coordinates (_x_, _y_) holding numeric values _z_. To compute contours on gridded coordinates, see d3-contour instead. To compute contours on geographic data, see d3.geoContour.

For examples, see the tricontours collection on Observable.

Installing

If you use npm, npm install d3-tricontour. You can also download the latest release on GitHub. For vanilla HTML in modern browsers, import d3-tricontour from Skypack:

``html

`

For legacy environments, you can load d3-tricontour’s UMD bundle from an npm-based CDN such as jsDelivr; a d3 global is exported:

`html




`

API Reference

The API of tricontour is similar to that of d3-contour:

# d3.tricontour() · Source, Examples

Constructs a new tricontour generator with the default settings.


# _tricontour_(_data_) · Examples

Returns an array of contours, one for each threshold. The contours are MultiPolygons in GeoJSON format, that contain all the points with a value larger than the threshold. The value is indicated as _geometry_.value.

The _data_ is passed as an array of points, by default with the format [x, y, value].

# _tricontour_.contour(_data_[, _threshold_])

Returns a contour, as a MultiPolygon in GeoJSON format, containing all points with a value larger or equal to _threshold_. The threshold is indicated as _geometry_.value

# _tricontour_.contours(_data_)

Returns an iterable over the contours.


# _tricontour_.isobands(_data_)

Returns an iterable over the isobands: contours between pairs of consecutive threshold values _v0_ (inclusive) and _v1_ (exclusive). _geometry_.value is equal to _v0_, _geometry_.valueMax to _v1_.


# _tricontour_.x([_x_])

Sets the x accessor. Defaults to \d => d[0]\. If _x_ is not given, returns the current x accessor.

# _tricontour_.y([_y_])

Sets the y accessor. Defaults to \d => d[1]\. If _y_ is not given, returns the current y accessor.

# _tricontour_.value([_value_])

Sets the value accessor. Defaults to \d => d[2]\`. Values must be defined and finite. If _value_ is not given, returns the current value accessor.

# _tricontour_.thresholds([_thresholds_])

Sets the thresholds, either explicitly as an array of values, or as a count that will be passed to d3.ticks. If empty, returns the current thresholds.

_The following are experimental_

These methods are used in d3-geo-voronoi’s geoContour.

# _tricontour_.triangulate([_triangulate_])

Sets the triangulate function. Defaults to d3.Delaunay.from. For detailed examples, see Reusing a tricontour triangulation, UK tricontour, and Multipolygon tricontour.

# _tricontour_.pointInterpolate(_[pointInterpolate]_)

Sets the pointInterpolate function. Arguments: i, j, 0≤a<1. Defaults to linear interpolation between the coordinates of points i and j.

# _tricontour_.ringsort(_[ringsort]_)

Sets the ringsort function.