K-nearest-neighbor shrink

Replace each voxel by the mean of its k nearest neighbors in its local spatial neighborhood.

Usage

knn_shrink(bvec, mask, k = 5, connectivity = 27)

Arguments

bvec

A NeuroVec instance (the data).

mask

A NeuroVol mask defining the voxels to include. If numeric, nonzero = included.

k

The number of nearest neighbors to average over.

connectivity

The number of spatial neighbors to include in the search around each voxel.

Value

A SparseNeuroVec or similar object with the smoothed data.

Examples

if (FALSE) { # \dontrun{
mask <- neuroim2::NeuroVol(array(1, c(20,20,20)), neuroim2::NeuroSpace(c(20,20,20)))
bvec <- replicate(10,
                  neuroim2::NeuroVol(array(runif(20*20*20), c(20,20,20)),
                           neuroim2::NeuroSpace(c(20,20,20))),
                  simplify=FALSE)
bvec <- do.call(neuroim2::concat, bvec)
sbvec <- knn_shrink(bvec, mask, k=3)
} # }