read Landmarks from Slicer in Json format
read.slicerjson(x, lps2ras = FALSE, na = NULL)returns matrix or list of matrices with imported landmark coordinates
path to json file
logical: if the coordinate system is LPS and lps2ras=TRUE, the data will be rotated into the RAS space by inverting the first two dimensions using LPS2RAS.
value to be replaced by NA