ptest: Permutation test for group differences at within-subject levels

Description

Perform permutation tests for differences between two groups at given within-subject levels in a long-formatted dataframe

Usage

ptest(
  data,
  outcome,
  within,
  between,
  at.within,
  at.between,
  pn = 1000,
  progress.bar = TRUE
)

Arguments

data

dataframe that contains the data in long format.

outcome

outcome variable (i.e., the variable for which the difference should be tested).

within

within-subject variable.

between

between-subjects variable.

at.within

determine for which within-subject levels (e.g., which timepoint) the difference should be tested.

at.between

determine the groups in the difference test (should always be of length 2).

the number of permutations that should be performed.

progress.bar

indicates whether a progress bar will be shown.

Value

ptest produces an object of class "clusbootptest", containing the following relevant components:

perm.statistics

A matrix of length(at.within) rows and pn columns, containing the Welch t-test statics for all permutations within the at.within level in the columns. The first column contains the t statistic for the observed data.

pvalues

Data frame containing the p values for every at.within level.

Details

In every permutation cycle, the outcome variable gets permutated and the Welch t test statistic is calculated.

Examples

Run this code

# NOT RUN {
medication <- medication[medication$time %% 1 == 0,]
set.seed(1)
permtest.1 <- ptest(data = meds, outcome = pos, within = time, between = treat, 
                    at.within = c(0,2,4,6), at.between = c(0,1), pn = 2000)
permtest.1$pvalues
# }