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I need to perform something similar to the ArcGIS tool for neighbourhood analysis (Toolbox>Spatial Analyst Tools>Neighorhood>Focal Statistics).

But for nearest neighbor in QGIS I need a point layer but I have just a raster TIFF. This is what I did so far:

I created a raster out of village polygons with value 1 for village and value 0 for novillage (via r.null). Now I want to know which and how many rastercells with novillage value (0) have one or several rastercells with village value (1) in a radius of 1500 m. If I need to convert the TIFF to a point layer, there are two questions: How to do it? How to keep the boundaries of my 25x25m grid if I tranform the grid to a point layer?

Please keep in mind I am quite new to QGIS.

I have QGIS Hanover 3.16 on a Linux Mint installed.

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    Is it absolutely mandatory to use raster files? Couldn't you just create a vector buffer of 1500 meters around the village?
    – gvanhavre
    Commented Jun 6, 2021 at 10:15
  • Thanks for fast reply! In further steps though I need to identify the size of nonvillage grid which dont have the village in the near distance of 1500 m for then appying a selection with other features to find out the best habitat for an animal. Maybe I could do this with a buffer as well and deselect somehow the grid within the buffer zone. But somehow I made a mistake anyways: because now in r.neighbor i can select my raster layer. I dont know why beforehand it only showed point layers. Therefor I think this should work now and I check if buffers might be the easier version. Thanks again!
    – Flynx
    Commented Jun 6, 2021 at 10:37

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Using a point layer, you can not keep the boundaries at the same time within the same layer. But you can create two layers out of your raster: a point layer and a polygon layer.

For this to do, there are two convenient processing tools available:

  • Raster pixels to points
  • Raster pixels to polygons

enter image description here

For your goal, in this answer I suggest to use the polygons. Because you can use this handy expression which counts the number of neighboring (touching) polygons having a 1 as value:

array_length(overlay_touches(@layer,$id,filter:="VALUE"=1,limit:=-1))

Change "VALUE" to the fieldname containing your values, by default the output of raster pixels to polygons calls it that way. Similary, you could also take the non-touching into account and instead use a distance limit as follows:

array_length(overlay_nearest(@layer,$id,filter:="VALUE"=1,limit:=-1,max_distance:=1500))

Note that limit:=-1 should return all results as stated in the documentation of this expression, but I encountered that this is not the case in v3.18.2, so also try changing -1 to e.g. 9999 or something like that if you encounter the same behavior in 3.16.

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  • Great, thanks for that suggestion and explanation! Much appreciated:) Also, I dont know if I somehow need to close this question since its answered?
    – Flynx
    Commented Jun 8, 2021 at 10:31

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