permTest {pARI}

Permutation Test

Description

Performs permutation-based two-sample t-tests.

Usage

permTest(X, B = 1000, alternative = "two.sided", seed = NULL, 
mask = NULL, rand = FALSE, label = NULL)

Arguments

X

data matrix where rows represent the m variables and columns the n observations.

B

numeric value. Number of permutations, default to 1000.

alternative

character string. It refers to the alternative hypothesis, must be one of "two.sided" (default), "greater" or "lower".

seed

integer value. If you want to specify the seed. Default to @NULL

mask

NIfTI file or character string. 3D array of logical values (i.e. TRUE/FALSE in/out of the brain). Alternatively it may be a (character) NIfTI file name. If mask=NULL, it is assumed that non of the voxels have to be excluded.

rand

Boolean value. Default @FALSE. If rand = TRUE, the p-values are computed by rowRanks.

label

numeric/character vector. Labels of the observations, if NULL the columns's name are considered. Default @NULL.

Value

Returns a list with the following objects: - Test: vector with length equals m. Observed two-samples t-tests, one for each m variable, - Test_H0: matrix with dimensions m \times B-1. Test statistics under H0, - pv: vector with length equals m. observed p-values, one for each m variable, - pv_H0 matrix with dimensions m \times B-1. P-values under H0.

Author(s)

Angela Andreella

Examples

X <- matrix(rnorm(100*20), ncol=20)
X[,1:10] <- X[,1:10] + rnorm(100*10, mean = 5)
out <- permTest(X = X, alternative = "two.sided", label = c(rep(1,10),rep(0,10)))