It is not currently possible to assign NoData to a post map outside of a polygon, but there is a workaround.
- Select your map.
- Click Home | Add to Map | Layer | Base from Data.
- Select the data file used to create your post map, and click Open.
- Set the data row and column properties in the Base from XY Data dialog, then click OK.
- In the Contents window, right click on the Base(vector) layer containing your points and click Start Editing.
- Click and drag your mouse around groups of points on the map which are outside of the polygon to mass-select them, and press DELETE on your keyboard to delete them.
- When all points outside of the polygon are removed, in the Contents window, right click on the Base(vector) layer containing your points and click Stop Editing.
- In the Contents window, uncheck the boxes next to everything except the base layer containing your points and the map containing that base layer, so only the points are visible.
- Click File | Export.
- In the Export dialog, change the Save as type to DAT XYZ (*.dat, *.txt, *.xyz), give your file a name, and click Save.
- In the Export Options dialog, on the Scaling page set the Scaling source to your Map.
- Click OK to create the DAT file.
- Click the File | Open command to open the DAT file in Surfer's worksheet.
- Select Column C and click Data | Data | Text to Number.
- Click File | Save to save the DAT file.
If you would like to add your vote to our suggestion file for a way to blank a post map outside of a polygon, contact firstname.lastname@example.org.
- How can I remove all points outside a polygon in Surfer?
- How can I interactively edit or remove points from a data set or post map in Surfer?
Updated October 25, 2018