Extract all post map points within a polygon in a base layer in Surfer

To assign NoData to a post map outside of a polygon:

1. Select your map.
2. Click Home | Add to Map | Layer | Base from Data.
3. Select the data file used to create your post map, and click Open.
4. Set the data row and column properties in the Base from XY Data dialog, then click OK.
5. In the Contents window, click on the Base(vector) layer.
6. If your area of interest or polygon is rectangular:
   1. Click Home | Selection | Select All | Block Select.
   2. Click and drag your mouse around the group of points on the map that you are interested in.
   3. Click Home | Selection | Select All | Invert Selection.
   4. Press DELETE on the keyboard to delete all selected points (outside the area of interest).
7. If your area of interest is not rectangular:
   1. In the Contents window, click the pin icon next to the Base layer to limit selection to that layer.
   2. Click on the base layer in the Plot window.
   3. Click and drag your mouse around groups of points on the map which are outside of the polygon to mass-select them
   4. Press DELETE on your keyboard to delete them.
   5. Repeat steps 7.3 & 7.4 until only the points you're interested in remain.  Alternatively, hold SHIFT while completing step 7.3 to select multiple groups of points before deleting.
8. In the Contents window, ensure the Base layer containing your points is selected.
9. Click File | Export.
10. In the Export dialog, check the box next to Selected objects only.
11. Change the Save as type to DAT XYZ (*.dat, *.txt, *.xyz), give your file a name, and click Save.
12. In the Export Options dialog, on the Scaling page set the Scaling source to your Map.
13. Click OK to create the DAT file.
14. Click the File | Open in Worksheet command to open the DAT file in Surfer's worksheet.
15. Select Column C and click Data | Data | Text to Number.
16. 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 surfersupport@goldensoftware.com. 

See also:

• Remove all points outside a polygon in a Surfer Post map or Base map
• Interactively edit/remove points from a data set or post map in Surfer

Updated December 20, 2021