5

I have two polygons that consist of two separate polygons/lines in QGIS). How can I make this into a multipart polygon, which consists of 1 line in QGIS?

4

Select your features.

  1. From Advanced Editing Toolbar, Click Merge Selected Features icon. enter image description here
  2. A dialog would pop up. Now select the record that you want to accept as the common record for your selected features. Click OK.
2

Vector->Geometry Tools->Single parts to Multipart

However, you say that you only want a multipart polygon consisting of a single line. You are unlikely to get that ever because that would be a single polygon, because, by definition, any multipart geometry has multiple parts.

You could also dissolve your data and that will create a multipart if you dissolve polygons which do not intersect but will also combine polygons which do intersect into single units and perhaps this is what you meant (Vector->Geoprocessing Tools->Dissolve)

  • what I mean by "1 line" is the attributes table. because I have 2 polygones on the same level it consists of two lines with data. so if I make them a multipart the attributes table would make one line with data right? – Michelle Hennekes Feb 21 '13 at 15:34
  • I tried what you said, it's not working. is that because both lines are in the same shape?... – Michelle Hennekes Feb 21 '13 at 15:36
  • By 'both lines' I assume you mean two separate attribute table records? If so could you refer to them as either 'records' or 'features' to avoid confusion with a line (as in geometry)? When you say it is not working can you be more explicit. Did you get an error? Did you try and dissolve or go single part to multipart? – MappaGnosis Feb 21 '13 at 15:48
  • indeed, I mean records or features, sorry for the confusion. This is the first time I'm working with Qgis. Qgis asks for a buffer, but I don't know what to do there... – Michelle Hennekes Mar 4 '13 at 15:12
2

For anyone coming to this with newer versions of QGIS, the function to do it is now called "Collect Geometries" rather than "Single parts to Multipart" so it's now Vector > Geometry Tools > Collect Geometries. You can then choose a field (or fields) to use as your grouping variable (Unique ID Fields). I used it to fix up some statistical areas which included non-contiguous polygons (islands in fact) where I'd ended up with 1 record for each separate polygon, but wanted 1 record for each statistical area. The reason I needed THAT was because I'm joining it to data in Tableau and ended up with a whole bunch of duplication happening around the coast due to the islands.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.