Skip to contents

Prunes mesh by eliminating long edges and small connected components

Source: R/utils_initdata.R
prune_graph.Rd

Pruning works in three steps:

  1. Any triangle with an edge longer than a threshold length is removed. Afterwards, any edge that no longer belongs to a triangle is removed. Then any point that no longer belongs to an edge is removed.

  2. Connected components of triangles with a shared edge are computed. If everything is connected, then nothing is pruned.

  3. Otherwise, components (and corresponding triangles) that contain less than mincells points are removed. Afterwards, any edge that no longer belongs to a triangle is removed. Then any point that no longer belongs to an edge is removed.

Usage

prune_graph(data, thresh_quantile = 0.95, mincells = 10, thresh = NA)

Arguments

data

A list containing the mesh data structures:

  • pts is a V-by-M data table with columns X and Y containing the coordinates of cells and additional metadata.

  • tris is a F-by-4 data table containing the X,Y coordinates of each triangle's centroid in the first two columns, and area and largest height of each triangle in the last two columns.

  • edges is a E-by-14 data table with columns from_pt, to_pt, from_tri, to_tri, x0_pt, x1_pt, y0_pt, y1_pt, x0_tri, x1_tri, y0_tri, y1_tri, length_pt, length_tri. If only one triangle uses an edge, then the from_tri, x0_tri, and y0_tri fields will contain NaN values.

  • tri_to_pt is a F-by-V sparse matrix with value 1 at (i,j) if triangle i uses point j as a vertex.

thresh_quantile

Floating point value between 0 and 1, inclusive. Quantile of edge length above which edges are pruned. Defaults to 0.95.

mincells

Minimum number of cells required for a connected component of triangles to be kept. Defaults to 10.

thresh

Edge length above which edges are pruned. If equal to NA, then this value is ignored and thresh_quantile is used to compute the threshold. Otherwise, if thresh is set, then thresh_quantile is ignored. Defaults to NA.

Value

A list containing the mesh data structures with (possibly) fewer points, edges, and triangles. Indices have been updated since some objects might have been removed.