brainwaver (version 1.6)

const.adj.mat: Computation of the adjacency matrix

Description

Computes the adjacency matrix for a given correlation matrix.

Usage

const.adj.mat(cor.mat, var.ind.mat = 0, n.ind = 0, thresh = 0.05, sup = 0,  test.method = "gaussian", proc.length, num.levels,  use.tanh = FALSE)

Arguments

cor.mat

matrix containing the correlation values. (must be diagonal with 1 on the diagonal)

var.ind.mat

matrix containing the variance inter individuals of the correlation. Only used with test.method="t.test". (default not used)

n.ind

number of individuals to take into account in the test. Only used with test.method="t.test". (default not used)

thresh

indicates the rate at which the FDR procedure is controlled. (default 0.05)

sup

indicates the correlation threshold to consider in each hypothesis test.

test.method

name of the method to be applied. "gaussian" assumes a gaussian law for the estimator. "t.test" implements a t.test for computing the p-value. (default "gaussian")

proc.length

specifies the length of the original processes using to construct the cor.mat

num.levels

specifies the number of the wavelet scale to take into account in the hypothesis test. Only used with test.method="gaussian"

use.tanh

logical. If FALSE take the atanh of the correlation values before applying the hypothesis test, in order to use the Fisher approximation

Value

Binary matrix.

Details

Each hypothesis test is written as :

$H_0$ : "|correlation| $<=$ sup"<="" p="">

$H_1$ : "|correlation| $>$ sup"

References

S. Achard, R. Salvador, B. Whitcher, J. Suckling, Ed Bullmore (2006) A Resilient, Low-Frequency, Small-World Human Brain Functional Network with Highly Connected Association Cortical Hubs. Journal of Neuroscience, Vol. 26, N. 1, pages 63-72.

See Also

const.adj.list

Examples

data(brain)
brain<-as.matrix(brain)
# WARNING : To process only the first five regions
brain<-brain[,1:5]


#Construction of the correlation matrices for each level of the wavelet decomposition
wave.cor.list<-const.cor.list(brain, method = "modwt" ,wf = "la8", n.levels = 6,
                               boundary = "periodic", p.corr = 0.975)

#Construction of the adjacency matrice for scale 4

adj.mat.4<-const.adj.mat(wave.cor.list[[4]], sup = 0.44,proc.length=dim(brain)[1], 
                          num.levels=4)

image(adj.mat.4,col=gray((0:20)/20))