extract_null_cluster_dists {jlmerclusterperm}

Construct a null distribution of cluster-mass statistics

Description

Construct a null distribution of cluster-mass statistics

Usage

extract_null_cluster_dists(null_statistics, threshold, binned = FALSE)

Arguments

null_statistics

A simulation-by-time-by-predictor 3D array of null (permuted) timewise statistics.

threshold

The threshold value that the statistic must pass to contribute to cluster mass. Interpretation differs on the choice of statistic (more below):

• If statistic = "t", the threshold for t-value (beta/std.err) from the regression model.

• If statistic = "chisq", the threshold for the p-value of chi-squared statistics from likelihood ratio tests.

binned

Whether the data has been aggregated/collapsed into time bins. Defaults to FALSE, which requires a cluster to span at least two time points. If TRUE, allows length-1 clusters to exist.

Value

A null_cluster_dists object.

See Also

permute_timewise_statistics()

Examples

library(dplyr, warn.conflicts = FALSE)

# Specification object
spec <- make_jlmer_spec(
  weight ~ 1 + Diet, filter(ChickWeight, Time <= 20),
  subject = "Chick", time = "Time"
)
spec

# Null cluster-mass distributions are derived from the permuted timewise statistics
reset_rng_state()
null_statistics <- permute_timewise_statistics(spec, nsim = 100)
null_cluster_dists <- extract_null_cluster_dists(null_statistics, threshold = 2)
null_cluster_dists

# Collect as dataframe with `tidy()`
# - Each simulation contributes one (largest) cluster-mass statistic to the null
# - When no clusters are found, the `sum_statistic` value is zero
null_cluster_dists_df <- tidy(null_cluster_dists)
null_cluster_dists_df

# Changing the `threshold` value changes the shape of the null
extract_null_cluster_dists(null_statistics, threshold = 1)
extract_null_cluster_dists(null_statistics, threshold = 3)