R：从栅格对象计算窗台，范围和块

I need to calculate the sill, range and nugget from a raster layer. I have explored gstat, usdm packages where one can create variogram however I couln't find a function which given a raster layer will estimate these parameters.In most of the functions these parameters have to be defined eg. krigging.I need to calculate the sill, range and nugget