Generate a table of all extended dimension attributes. For now that means interpretation of any "time" dimension.
nc_extended(x, ...)
# S3 method for class 'character'
nc_extended(x, ...)
# S3 method for class 'NetCDF'
nc_extended(x, ...)
# S3 method for class 'ncdf4'
nc_extended(x, ...)
data frame of extended dimension attribute information