vcg_kdtree_nearest: Find nearest 'k' points

In dipterix/ravetools: Signal and Image Processing Toolbox for Analyzing Intracranial Electroencephalography Data

Find nearest k points

Description

For each point in the query, find the nearest k points in target using K-D tree.

Usage

vcg_kdtree_nearest(target, query, k = 1, leaf_size = 16, max_depth = 64)

Arguments

target	a matrix with n rows (number of points) and 2 or 3 columns, or a mesh3d object. This is the target point cloud where nearest distances will be sought
query	a matrix with n rows (number of points) and 2 or 3 columns, or a mesh3d object. This is the query point cloud where for each point, the nearest k points in target will be sought.
k	positive number of nearest neighbors to look for
leaf_size	the suggested leaf size for the K-D tree; default is 16; larger leaf size will result in smaller depth
max_depth	maximum depth of the K-D tree; default is 64

Value

A list of two matrices: index is a matrix of indices of target points, whose distances are close to the corresponding query point. If no point in target is found, then NA will be presented. Each distance is the corresponding distance from the query point to the target point.

Examples

# Find nearest point in B with the smallest distance for each point in A

library(ravetools)

n <- 10
A <- matrix(rnorm(n * 2), nrow = n)
B <- matrix(rnorm(n * 4), nrow = n * 2)
result <- vcg_kdtree_nearest(
  target = B, query = A,
   k = 1
)

plot(
  rbind(A, B),
  pch = 20,
  col = c(rep("red", n), rep("black", n * 2)),
  xlab = "x",
  ylab = "y",
  main = "Black: target; Red: query"
)

nearest_points <- B[result$index, ]
arrows(A[, 1],
       A[, 2],
       nearest_points[, 1],
       nearest_points[, 2],
       col = "red",
       length = 0.1)

# ---- Sanity check ------------------------------------------------
nearest_index <- apply(A, 1, function(pt) {
  which.min(colSums((t(B) - pt) ^ 2))
})

result$index == nearest_index

dipterix/ravetools documentation built on March 5, 2025, 3:08 a.m.