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I am looking for a way in QGIS (1.8.0) to visualise data, which is related to an area (polygon on a shape file). There are no x-y-coordinates with the data, just the info of the belonging area, means at an arbitrary position inside the area.

Example: Samples x1,x2 and x3 are located in area a1, y1 to y5 in area a2.

As the samples have certain properties on which I intend to do queries on, distinct locations seems somehow necessary (e.g. sample x1 and x3 have a certain property and therefore should be shown/highlighted ).

I initially thought of assigning each sample some random coordinates from inside the areas, but what a hassle..

So, how to approach that??

  • Yes, QGIS (1.8.0), forgot to mention that. – nick Aug 29 '13 at 12:54
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    Do you want to show the values of x1,x2 and x3 separately or do you want to aggregate them to create a new value for area a1? – underdark Aug 29 '13 at 16:58
  • I would definitely prefer to show them separately (like data points having coordinates). When a query has a positive match on sample x1 and x3, it should be somehow be indicated that there are two matches in in area a1. – nick Aug 30 '13 at 6:27
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What I think you're looking for is a foreign key relationship between your (spatial) areas and your (non-spatial) samples. This answer may be of use: One to Many Relationship in QGIS with PostGIS, but is rather PostGIS-specific. You can do this in QGIS with a join relationship between a shapefile attribute and a plain table.

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  • Thanks scruss. I will start simple and look into the join relationship (however that is going to visualise when called through a query...) – nick Aug 29 '13 at 14:16
  • OK. I found a tutorial which explains the join relationship issue nicely. Now, with my one-to-many problem, it seems I will not be able to avoid going into a database... But that is probably preferable, it needs to be of a dynamic nature as the dataset will grow during the next years.. – nick Aug 29 '13 at 14:53

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