postsamples {BHMSMAfMRI} | R Documentation |
Obtain samples from the posterior distribution of a 2D GLM coefficient map.
Description
postsamples
generates samples from the posterior distribution of a 2D GLM coefficient map (e.g., corresponding to a single brain slice) of a regressor in the BHMSMA model for each subject based on multi-subject or single subject analyses (see References).
Usage
postsamples(nsample, n, grid, glmcoefstd, waveletcoefmat,
hyperparam, pkljbar, analysis, wave.family="DaubLeAsymm",
filter.number=6, bc="periodic", seed)
Arguments
nsample |
Number of samples to be generated. |
n |
Number of subjects. |
grid |
The number of voxels in one row (or, one column) of the brain slice of interest. Must be a power of 2. The total number of voxels is |
glmcoefstd |
An array of dimension |
waveletcoefmat |
A matrix of dimension |
hyperparam |
A vector containing the estimates of the six hyperparameters. |
pkljbar |
A matrix of dimension |
analysis |
"MSA" or "SSA", depending on whether performing multi-subject analysis or single subject analysis. |
wave.family |
The family of wavelets to use - "DaubExPhase" or "DaubLeAsymm". Default is "DaubLeAsymm". |
filter.number |
The number of vanishing moments of the wavelet. Default is 6. |
bc |
The boundary condition to use - "periodic" or "symmetric". Default is "periodic". |
seed |
Must be a positive integer. Provide to set random number generation seed for reproducibility. |
Details
The wavelet computations are performed by using the R package wavethresh.
Value
A list containing the following.
samples |
An array of dimension |
postdiscovery |
An array of dimension |
Author(s)
Nilotpal Sanyal, Marco Ferreira
Maintainer: Nilotpal Sanyal <nilotpal.sanyal@gmail.com>
References
Sanyal, Nilotpal, and Ferreira, Marco A.R. (2012). Bayesian hierarchical multi-subject multiscale analysis of functional MRI data. Neuroimage, 63, 3, 1519-1531.
Morris, J.S. et al. (2011). Automated analysis of quantitative image data using isomorphic functional mixed models, with application to proteomic data. Ann. Appl. Stat. 5, 894-923.
See Also
readfmridata
, glmcoef
, waveletcoef
, hyperparamest
, postmixprob
, postwaveletcoef
, substituteWaveletCoef
, postglmcoef
, imwd
, imwr
Examples
set.seed(1)
n <- 3
grid <- 8
nsample <- 5
glmcoefstd <- array(rnorm(n*grid*grid),
dim=c(n,grid,grid))
waveletcoefmat <- array(rnorm(n*(grid^2-1)),
dim=c(n,(grid^2-1)))
hyperparam <- rep(.2,6)
pkljbar <- array(runif(n*(grid^2-1)),
dim=c(n,(grid^2-1)))
analysis <- "multi"
postsample <- postsamples(nsample,n,grid,glmcoefstd,
waveletcoefmat, hyperparam,pkljbar,analysis,seed=1)
dim(postsample$samples)
#[1] 3 8 8 5