TTfast: TTfast

In dorianps/LESYMAP: Lesion to Symptom Mapping in R

TTfast

Description

Compiled fast t-tests on matrices. Takes a binary matrix X with zero and non-zero values, and a matrix Y of continuous values. Computes the t-test on each Y column using the respective X column to define the two groups. If Y is a matrix with one column, that column is used to test with grouping derived from every column in X. This function is used in LESYMAP with a binarized X matrix derived from lesioned voxels in the brain.

Usage

TTfast(X, Y, computeDOF = TRUE, varEqual = TRUE)

Arguments

X	binary matrix of voxels (columns) for all subjects (rows).
Y	matrix of behavioral scores of same size as X or a matrix with a single column.
computeDOF	(default=true) chooses whether to compute degrees of freedom. Set to false to save time during permutations.
varEqual	(default=true) chooses whether to compute Student t-scores (true) or Welch d-scores (false). The only difference is the assumption on variance which for t-scores must be satisfied. This assumption is often violated in some voxels, and the use of Welch (varEqual=false) is recommended for more accurate results.

Value

List with two vectors:

• statistic - Student T or Welch D

• df - degrees of freedom

Author(s)

Dorian Pustina

Examples

set.seed(1234)
lesmat = matrix(rbinom(60,1,0.2), ncol=2)
set.seed(12345)
behavior = cbind( rnorm(30) )
set.seed(123456)
behavior = cbind ( behavior, rnorm(30) )
test = LESYMAP::TTfast(lesmat, behavior)
test$statistic[,1] # -2.359317  1.040766

dorianps/LESYMAP documentation built on June 1, 2024, 2:12 a.m.