initial {MixfMRI} | R Documentation |
Main initialization functions
Description
Main initialization functions.
Usage
initial.em.gbd(PARAM)
initial.RndEM.gbd(PARAM)
Arguments
PARAM |
a list of uninitialized parameters, as usual, the returned
values of |
Details
initial.em.gbd()
takes in a template of PARAM
(uninitialized),
and usually is available by calling set.global()
, then
return an initialized PARAM
which is ready for EM runs.
Internally, there are six different initializations implemented for
the function initial.em.gbd()
including prob.extend
,
prob.simple
, qnorm.extend
, qnorm.simple
, extend
,
and simple
. These methods are mainly based on transformation of
original space of data (p-values and voxel locations) into more linear
space such that the Euclidean distance more makes sense (fairly) to
classify data in groups.
initial.RndEM.gbd()
implement RndEM initialization algorithm
based on repeated calling initial.em.gbd()
.
Note that all configurations are included in PARAM
set by
set.global()
.
Value
These functions return an initialized PARAM
for EM runs based on
pre-stored configuration within the input uninitialized PARAM
.
Author(s)
Wei-Chen Chen and Ranjan Maitra.
References
Chen, W.-C. and Maitra, R. (2021) “A Practical Model-based Segmentation Approach for Accurate Activation Detection in Single-Subject functional Magnetic Resonance Imaging Studies”, arXiv:2102.03639.
See Also
set.global()
, fclust()
, PARAM
.
Examples
library(MixfMRI, quietly = TRUE)
library(EMCluster, quietly = TRUE)
# .FC.CT$algorithm <- "em"
# .FC.CT$model.X <- "V"
# .FC.CT$ignore.X <- TRUE
.FC.CT$check.X.unit <- FALSE
### Test toy1.
set.seed(1234)
X.gbd <- toy1$X.gbd
PV.gbd <- toy1$PV.gbd
PARAM <- set.global(X.gbd, PV.gbd, K = 2)
PARAM.new <- initial.em.gbd(PARAM)
PARAM.toy1 <- em.step.gbd(PARAM.new)
id.toy1 <- .MixfMRIEnv$CLASS.gbd
print(PARAM.toy1$ETA)
RRand(toy1$CLASS.gbd, id.toy1)
.rem <- function(){
### Test toy2.
set.seed(1234)
X.gbd <- toy2$X.gbd
PV.gbd <- toy2$PV.gbd
PARAM <- set.global(X.gbd, PV.gbd, K = 3)
PARAM.new <- initial.em.gbd(PARAM)
PARAM.toy2 <- em.step.gbd(PARAM.new)
id.toy2 <- .MixfMRIEnv$CLASS.gbd
print(PARAM.toy2$ETA)
RRand(toy2$CLASS.gbd, id.toy2)
}