In real application, we usually want to test multiple features. For example,
test.data <- matrix(rnorm(100),nrow=10,ncol=10)
colnames(test.data) <- paste('feature',1:10,sep='')
rownames(test.data) <- paste('sample',1:10,sep='')
test.data
we want to compare the sample 1-5 vs. sample 6-10 for each feature. We need a wrapper function for this.