Usage
## S3 method for class 'dtiData':
dwi.smooth(object, kstar, lambda=20, kappa0=NULL, ncoils=1,
sigma=NULL, level=NULL, vred=4, xind=NULL,
yind=NULL, zind=NULL, verbose=FALSE, dist=1,
model=c("Gapprox","Gapprox2","Chi","Chi2"))
## S3 method for class 'dtiData':
dwi.smooth.ms(object, kstar, lambda=12, kappa0=.5, ncoils=1,
sigma=NULL, ws0=1, level=NULL, mask = NULL, xind=NULL,
yind=NULL, zind=NULL, verbose=FALSE,
usemaxni=TRUE, memrelease = TRUE)Arguments
object
Object of class "dtiData"
kstar
Number of steps in structural adaptation
lambda
Scale parameter in adaptation
kappa0
determines amount of smoothing on the sphere. Larger values correspond to stronger smoothing on the sphere. If kappa0=NULL a value is that corresponds to a variace reduction with factor vred on the sphere.
ncoils
Number of coils in MR system
sigma
Error standard deviation. Assumed to be known and homogeneous in the current implementation. A reasonable estimate may be defined
as the modal value of standard deviations obtained using method getsdofsb.
level
Threshold for image intensities when setting mask.
mask
Binary 3D image defining a mask
vred
Used if kappa0=NULL to specify the variance reduction on the sphere when suggesting a value of kappa0
xind
index for x-coordinate
yind
index for y-coordinate
zind
index for z-coordinate
verbose
If verbose=TRUE additional reports are given.
dist
Distance in SE3. Reasonable values are 1 (default, see Becker et.al. 2012), 2 ( a slight modification of 1: with k6^2 instead of abs(k6)) and 3 (using a 'naive' distance on the sphere)
model
Determines which quantities are smoothed. Possible values are
"Chi" for observed values (assumed to be distributed as noncentral
Chi with 2*ncoils degrees of freedom), "Chi2" for squares of
observed values (ass
ws0
Factor to downweight information from S0 images, defaults
to 1/numer of s0 images.
usemaxni
If "usemaxni==TRUE" a strikter penalization is used.
memrelease
If "memrelease==TRUE" try to release allocated memory whenever possible.