| 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) |