R/group_xyz.R

In neuroconductor-devel/spm12r: Wrapper Functions for 'SPM' (Statistical Parametric Mapping) Version 12 from the 'Wellcome' Trust Centre for 'Neuroimaging'

#' @title Center of Gravity for Multiple Areas
#' @description Find Center of Gravity of Each Area of Image, after thresholding
#' @param img Object of class nifti
#' @param k Minimum number of voxels for a cluster.  
#' See \code{\link{spm_bwlabel}}
#' @param ... Arguments passed to \code{\link{spm_bwlabel}}
#' @return Matrix of 3 columns
#' @importFrom neurobase xyz
#' @export
group_xyz = function(img, k = 1, ...){
  les_xyz = spm_bwlabel(
    img,
    binary = FALSE,
    retimg = TRUE,
    k = k,
    ...)
  les_levs = sort(unique(les_xyz[les_xyz != 0]))
  if (length(les_levs) <= 1) {
    return(t(xyz(les_xyz)))
  } else {
    les_xyz = t(sapply(les_levs, function(x){
      xyz(les_xyz == x)
    }))
    return(les_xyz)
  }
  return(les_xyz)
}