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I have a project with two layers:

  1. A work area as a single polygon
  2. A set of points all contained in the previous area

I would like to divide the original area into 5 polygons/features that all contain the same amount of points from the second layer.

The pink area is the one to divide and the greet points should be equally distributed on the new divisions

So far the closest thing I found was the answer to How to group points in QGIS? which suggests using the Concave Hull plugin but I haven't found a way to specify how many groups I want with that tool.

So, what I would like to end up with is 5 polygons that contain 116 or 117 points each and which ideally cover only the pink area.

If you would like to try with my data, it can be accessed here.

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Edsonytic
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1 Answers1

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If it's really just five, I would do it by hand.

  1. Select as many points as you want — you can use the freehand select tool to have more control over the shape.
  2. Generate a hull for them.
  3. Cut the main polygon to match (union, intersection, difference, so many choices with more or less extra work) and dissolve parts together as needed.
  4. Repeat for the remaining four subgroups.
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lynxlynxlynx
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  • I might be understanding everything wrong (I'm very new to GIS) but I don't think this would have the desired outcome. What I need is to divide the original polygon into five parts which taken together wold still represent the original area. The criteria for division should be that each new division contains the same amount of points from the second layer (583 points / 5 divisions = 116.6 points per division) – Edsonytic Oct 18 '16 at 04:12
  • Continuing my previous comment:

    I see this problems

    Even when I try selecting all the points the resulting hull does not cover all of the original area https://i.stack.imgur.com/vCBa9.png

    The points only have an ID and they are not ordered in space so when selecting through the attribute table I basically get spatialy random points [2]: https://i.stack.imgur.com/4epkM.png

    This is sort of what I would like to get, only I cut those differently coloured parts by hand ignoring the points https://i.stack.imgur.com/Urtfi.png

     – Edsonytic Oct 18 '16 at 04:38
  • Yeah, I understood you. That's the third step, where after you get each mini hull, you merge and cut the base polygon, so the relevant difference is added to the starting hull. – lynxlynxlynx Oct 18 '16 at 20:41
  • I really took my time to answer this time in order to try out your method but either I'm really not understanding an essential part of the method or it doesn't do what I want. The nearest I got to the desired outcome was having five sections of the original area cut out based on the concave hulls. However there where always parts of the original which had not been included into any of the new sections. – Edsonytic Oct 31 '16 at 02:59
  • Does this crude drawing help? http://lynxlynx.info/gis/subhulls.gif – lynxlynxlynx Nov 02 '16 at 23:30