4

I try my best to explain my problem in english:

We use QGIS. We have a shapefile that shows a city divided in 277 areas. We have computed the centroids of each of these areas. Next step we have georeferenced adresses of general practitioners. Then we made a buffer around each general practitioners.

Now we'd like to have a new column in our attribute table that shows, for each area centroid, by how many buffers it is covered. We have tried to solve it with the field calculator to use "sum" without success.

4

Another option using refFunctions plugin is to:

  1. Install refFunctions plugin.
  2. Open attribute table of the centroid layer. Create a new field by an expression intersecting_geom_count('Buffer') (if your buffer layer is named Buffer).

enter image description here

2

There's a nice an easy inbuilt way to do this in QGIS 3.0:

  • From the Processing Toolbox, search for the "Join attributes by location (summary)" algorithm
  • Select your centroid layer as the "Input layer"
  • Select the buffer layer as the "Join layer"
  • Make sure "intersects" is ticked
  • Click the "..." button next to "Fields to summarise" and tick only one unique field from your buffer layer (e.g. a feature id field)
  • Click the "..." button next to "summaries to calculate" and tick only "count"

Run the algorithm. You'll get a new layer with the centroids and all their original features, plus a new field containing the count of intersectings buffer polygons.

1

One way is to intersect the centroid and buffers, this should give layer containing every intersection, then dissolve the new layer with a unique field from the centroid and use sum on a unique field from the buffer

  • I think we have the layer containing every intersection. But how to dissolve this layer? – user121171 May 22 '18 at 12:08
  • can you post the layer? – neogeomat May 22 '18 at 12:13
  • I´m sorry I can´t. But I ask my project partner for help. We write later again – user121171 May 22 '18 at 12:29

Your Answer

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