Create a Binary Label Adjacency Matrix (All Pairs)

Constructs a binary adjacency matrix based on two sets of labels `a` and `b`, creating edges for ALL pairs (i, j) where labels match (type="s") or differ (type="d"). This computes the full cross-product comparison between the two label vectors.

Usage

binary_label_matrix(a, b = NULL, type = c("s", "d"))

Arguments

a

A vector of labels for the first set of data points.

b

A vector of labels for the second set of data points (default: NULL). If NULL, `b` will be set to `a`.

type

A character specifying the type of adjacency matrix to create, either "s" for same labels or "d" for different labels (default: "s").

Value

A sparse binary adjacency matrix of dimensions (length(a) x length(b)) with 1s where the label relationship holds.

Details

For type="s", the result is a block-diagonal structure when a==b, with blocks corresponding to each class. For type="d", the result is the complement.

This function uses efficient sparse matrix multiplication via indicator matrices, avoiding O(n^2) memory usage from expanding all pairs.

See also

diagonal_label_matrix for element-wise (positional) comparison

Examples

data(iris)
a <- iris[,5]
bl <- binary_label_matrix(a, type="d")