Skip to contents

Find Isolated Pixels in Grid

find_isolated_pixels.Rd

Scans the grid to find black pixels that have no black neighbors, which violates the connectivity requirement for DLA simulations.

Usage

find_isolated_pixels(grid, neighborhood = "4-hood")

Arguments

grid

Numeric matrix representing the grid state (0 = white, 1 = black)

neighborhood

Character string specifying neighborhood type: "4-hood" (orthogonal) or "8-hood" (includes diagonals)

Value

List of isolated pixel positions (each element is a 2-element numeric vector with row and column indices). Returns empty list if no isolated pixels found.

Details

This function is useful for:

  • Debugging WebR/Shiny reactive timing issues

  • Validating grid state after async simulations

  • Testing grid connectivity requirements

A pixel is considered isolated if:

  • It is black (value = 1)

  • None of its neighbors (in the specified neighborhood) are black

Note: The center pixel is never considered isolated (it's the seed).

See also

validate_termination_position, validate_no_isolated_pixels

Examples

grid <- initialize_grid(10)
#> INFO [2026-02-03 16:36:04] Initializing grid of size 10x10
grid[3, 3] <- 1  # Add isolated pixel far from center
isolated <- find_isolated_pixels(grid, "4-hood")
#> WARN [2026-02-03 16:36:04] Grid has 2 isolated pixel(s)
length(isolated)  # Should be 1
#> [1] 2