| grids | Spatial grid dataset. | 
| gsdvar | Generating second-dimension variables for a spatial variable | 
| obs | Spatial datasets of trace elements. | 
| rmvoutlier | Removing outliers. | 
| sample_vars_fda | Spatial datasets of the first dimension variables of trace elements. | 
| sample_vars_sda | Spatial datasets of the second dimension variables of trace elements. | 
| sdapredvars | Preparing explanatory variables data for SDA-based prediction | 
| selectvarlm | Selecting variables using linear regression | 
| selectvarsda | Selecting variables for the SDA model | 
| vif | Fast calculation of the variance inflation factor (VIF) |