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I have 2 shape files (1x points and 1x polygons). The points have different values (soil sampling results). What I want to do is to calculate the mean values of the points inside the different polygons (field border lines). In the end I can calculate percentaged values instead of the original values. These percentaged points I can interpolate. Usually I did this with the following steps:

  1. converting point shape to grid
  2. Zonal Statistics to get the mean values
  3. Calculating the percentaged values with the mean
  4. Converting raster to points
  5. Interpolation (e.g. kriging)

This takes a very long time because the model I built is very slow. Is there another helpful tool that I could use (Zonal Statistics with vector points and vector polygone)?

Bye!


I gave Open Jump a chance and it works. What do you think, will there be a tool like that (it works like Zonal statistics just with a point and a polygon vector layer) one day in QGis?

2 Answers 2

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If it does not need to be QGis I believe that Aggregation tool of OpenJUMP Plus can do exactly what you want. Tool is in Plugins - Analysis - Aggregation. With the selections used in the image below the tool adds a new column "Average" into the polygon layer and populates the field with average value of attribute "measure" of the points which are within each polygon.

enter image description here

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  • Sounds good but I dont want to use an extra GIS beside QGis.
    – Pimpel
    Feb 5, 2015 at 19:49
  • It is understandable. However, if you just need to get the job done this is one of the fastest methods. Another good alternative is to save the layers from QGis into PostGIS or Spatialite and do the analysis with SQL.
    – user30184
    Feb 5, 2015 at 19:55
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    @Pimpel please accept this answer if it solved your issue
    – underdark
    Jun 10, 2017 at 10:42
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At least first two steps could be done by v.vect.stats from GRASS tools. As far as I understand, this algorithm does exactly the same as OpenJump Aggregation tool. enter image description here

I'm getting average values of my point layer inside polygons which I can then convert to centroids and interpolate...

enter image description here

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