Compute barycentric coordinates — fm

Identify knot intervals or triangles and compute barycentric coordinates

Usage

fm_bary(mesh, loc, ...)

# S3 method for fm_mesh_1d
fm_bary(mesh, loc, method = c("linear", "nearest"), restricted = FALSE, ...)

# S3 method for fm_mesh_2d
fm_bary(mesh, loc, crs = NULL, ...)

# S3 method for inla.mesh
fm_bary(mesh, ...)

# S3 method for inla.mesh.1d
fm_bary(mesh, ...)

Arguments

mesh: fm_mesh_1d or fm_mesh_2d object
loc: Points for which to identify the containing interval/triangle, and corresponding barycentric coordinates. May be a vector (for 1d) or a matrix of raw coordinates, sf, or sp point information (for 2d).
...: Arguments forwarded to sub-methods.
method: character; method for defining the barycentric coordinates, "linear" (default) or "nearest"
restricted: logical, used for method="linear". If FALSE (default), points outside the mesh interval will be given barycentric weights less than 0 and greater than 1, according to linear extrapolation. If TRUE, the barycentric weights are clamped to the (0, 1) interval.
crs: Optional crs information for loc

Value

A list with elements t; either

vector of triangle indices (triangle meshes),
matrix of interval knot indices (1D meshes), or
matrix of lower left box indices (2D lattices),

and bary, a matrix of barycentric coordinates.

Methods (by class)

fm_bary(fm_mesh_1d): Return a list with elements t (start and endpoint knot indices) and bary (barycentric coordinates), both 2-column matrices.

For method = "nearest", t[,1] contains the index of the nearest mesh knot, and each row of bary contains c(1, 0).
fm_bary(fm_mesh_2d): A list with elements t (vector of triangle indices) and bary (3-column matrix of barycentric coordinates). Points that were not found give NA entries in t and bary.

Examples

str(fm_bary(fmexample$mesh, fmexample$loc_sf))
#> List of 2
#>  $ t   : int [1:10] 331 303 425 342 377 223 365 92 92 359
#>  $ bary: num [1:10, 1:3] 0.316 0.137 0.485 0.292 0.625 ...
str(fm_bary(fm_mesh_1d(1:4), seq(0, 5, by = 0.5)))
#> List of 2
#>  $ t   : num [1:11, 1:2] 1 1 1 1 2 2 3 3 3 3 ...
#>  $ bary: num [1:11, 1:2] 2 1.5 1 0.5 1 0.5 1 0.5 0 -0.5 ...