Surfer's data filter allow you to filter data by X, Y, and Z variables as well as any column in the worksheet containing numeric data. To filter data by a worksheet column during gridding, follow the steps below.
- Click Home | Grid Data | Grid Data.
- In the Open Data dialog, select your data file and click Open.
- In the Grid Data dialog, click Filter Data.
- In the Filter dialog, enter the desired expression such as _E = -999. Where E is the desired worksheet column. The underscore differentiates worksheet columns from standard X, Y, or Z variables.
- Click OK.
- In the Grid data dialog, set the gridding parameters as desired.
- If desired, click Statistics to verify the filter is applied as desired.
- Click OK in the Grid Data dialog.
The same filters can be applied in the worksheet using the Data | Data | Spatial Filter command or when creating a variogram using the Grids | New Grid | Variogram | New Variogram command.