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embedding.rst

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Embedding: Embedding an abstract complex into space

simplicial

Embedding

Important

Embeddings are also used to support simplicial's drawing routines <drawing>.

Basic properties of the embedding space

The embedding space can have any number of dimensions, defaulting to two. (At present simplicial only supports Euclidian embedding spaces.)

Embedding.dimension

Embedding.origin

Embedding.complex

The locations give rise to a notion of distance between positions.

Embedding.distance

Positioning simplices

An embedding works by specifying the positions of the 0-simplices of a complex. Since all higher simplices have a basis constructed of 0-simplices, these positions then induce positions for all the higher-order simplices.

There are two ways to specify an embedding. The first is to provide explicit co-ordinates for every 0-simplex in a complex. This is very general but misses some frequent commonalities, and so the second way is to provide a sub-class of Embedding that overrides the Embedding.computePositionOf method. The two methods play well together: one can provide a sub-class to capture the regularities, and then perturb the complex by moving individual points if required. (Client code should only use Embedding.positionOf to access simplex positions, and not access to computation method directly. This ensures that explicit positions are returned correctly and cached.)

Embedding.positionSimplex

Embedding.computePositionOf

Embedding.positionOf

Embedding.positionsOf

Embedding.clearPositions

Dict-like interface

Embedding also exports a dict-like interface.

Embedding.__len__

Embedding.__getitem__

Embedding.__setitem__

Embedding.__contains__

Spatial constructions

Embeddings apply a geometry to a topological structure. It can be useful to go the other way: to take some geometric or spatial information and create a topological structure from it, where the topological structure encodes useful information. Typically this depends on a notion of distance between the located 0-simplices. The distance metric can then provide a way of constructing higher-dimensional simplices.

Embedding.vietorisRipsComplex