Permutation test for any metric between brain maps — permtest

Computes a user-specified metric between two vectors and tests significance using either spatially-constrained null surrogates or simple random permutation.

Usage

permtest_metric(
  x,
  y,
  metric_func = stats::cor,
  n_perm = 1000L,
  seed = NULL,
  null_method = NULL,
  distmat = NULL,
  coords = NULL,
  parcellation = NULL,
  ...
)

Arguments

x, y: Numeric vectors.
metric_func: Function taking (x, y) and returning a scalar.
n_perm: Integer number of permutations.
seed: Optional integer seed for reproducibility.
null_method: Optional null model method passed to generate_nulls(). If NULL, uses simple random permutation.
distmat: Distance matrix (passed to generate_nulls() if needed).
coords: Coordinate list (passed to generate_nulls() if needed).
parcellation: Integer vector (passed to generate_nulls() if needed).
...: Additional arguments passed to generate_nulls().

Value

List with $observed, $null_values, $p_value, and $n_perm.

References

Markello RD et al. (2022) Nature Methods 19:1472-1480. doi:10.1038/s41592-022-01625-w

Examples

x <- rnorm(100)
y <- x + rnorm(100)
result <- permtest_metric(x, y, n_perm = 99L, seed = 1L)
result$observed
#> [1] 0.6552005
result$p_value
#> [1] 0.01