R/fc_decompsigma.r

In MixfMRI: Mixture fMRI Clustering Analysis

### This file contains functions for decomposition of SIGMA of MVN.
### These will be majorly used in m.step() to update PARAM$U and PARAM$U.check.

decompsigma.I <- function(full, sigma.ill = .FC.CT$CONTROL$sigma.ill){
  DS <- sqrt(full)
  DS.check <- TRUE
  if(min(DS) / max(DS) < sigma.ill){
    .MixfMRIEnv$cat("Checks via min(DS)/max(DS) may have errors.\n", quiet = TRUE)
    DS.check <- FALSE
  }

  list(value = DS, check = DS.check)
} # End of decompsigma.I().

decompsigma.V <- function(full, sigma.ill = .FC.CT$CONTROL$sigma.ill){
  DS <- try(chol(full), silent = TRUE)
  if(inherits(DS, "try-error")){
    .MixfMRIEnv$cat("Checks via chol() may have errors.\n", quiet = TRUE)
    DS.check <- FALSE
  } else{
    ds <- diag(DS)
    DS.check <- TRUE
    if(any(ds < .MixfMRIEnv$CONTROL$DS.min |
           ds > .MixfMRIEnv$CONTROL$DS.max)){
      DS.check <- FALSE
    }
  }

  list(value = DS, check = DS.check)
} # End of decompsigma.V().