tricontours

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.

For examples, see the contours collection on Observable.

Installing

If you use NPM, npm install tricontours. Otherwise, download the latest release. You can also load directly as a standalone library. ES modules, AMD, CommonJS, and vanilla environments are supported. In vanilla, a tricontours global is exported:

``html




`

API Reference

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

# tricontours() · Source, Examples

Constructs a new tricontours generator with the default settings.

`js
const tri = tricontours();
`


# _tricontours_(_data_)

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].

# _tricontours_.contour(_data_[, _value_])

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

# _tricontours_.contours(_data_)

Returns an iterable over the contours.

# _tricontours_.isobands(_data_)

Returns an iterable over the isobands (contours between pairs of consecutive threshold values). _geometry_.value is equal to [value0, value1].

# _tricontours_.x([_x_])

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

# _tricontours_.y([_y_])

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

# _tricontours_.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.

# _tricontours_.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 still experimental_

# _tricontours_.triangulate([_triangulate_])

Sets the triangulate function. Defaults to d3.Delaunay.from. See UK tricontours for a detailed example.

# _tricontours_.pointInterpolate(_[pointInterpolate]_)

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