fcaR (version 1.5.0)

randomize_context: Randomize an Existing Formal Context

Description

Modifies the incidence matrix of a formal context to create a random variation while preserving certain statistical properties. This is essential for statistical significance testing in FCA (e.g., "is this concept structure random?").

Usage

randomize_context(fc, method = "swap", iterations = NULL)

Value

A new FormalContext object with the randomized incidence.

Arguments

fc

(FormalContext) The context to randomize.

method

(character) The randomization strategy:

• "swap": Edge Swapping (Curveball algorithm). Preserves exact row sums and column sums (marginal distributions). The structure changes, but the statistics of objects and attributes remain identical.

• "rewire": Edge Rewiring. Preserves only the global density (total number of 1s). Row and column sums may change.

iterations

(integer) Number of swap/rewire operations to perform. Default is 10 * number of 1s, which is usually sufficient for mixing.

Examples

data(planets)
fc <- FormalContext$new(planets)

# 1. Edge Swapping (Preserves degree distribution)
# Useful for null-model testing
fc_rand_swap <- randomize_context(fc, method = "swap")

# Verify marginals are preserved
colSums(fc$incidence())
colSums(fc_rand_swap$incidence())

# 2. Rewiring (Preserves only density)
fc_rand_rewire <- randomize_context(fc, method = "rewire")