I'm trying to classify a set of buildings (grey) in a layer, according to construction year, in a number of different areas (orange).

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In Orange – areas with a sum of buildings inside.

The construction year information is inside the area’s layer… Ok, so I think this is a problem with data display, because all my data is organized like this:

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So for Area D, there are 18 buildings built in 1940, and so on…

How can I classify this information to calculate maximum and show inside of each area what the most represented year is?

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    u want a calculation or a "graphic" display ? Why not colouring the buildings according to the construction year ? – snaileater Jun 2 '17 at 18:15
  • If you're up for some SQL Spatial, you can do this using shapefiles (i'm assuming you're using) with the QGIS DB Manager... – DPSSpatial Jun 2 '17 at 18:23
  • classify each building by its year and have a unique symbology (color) for each year (if there isn't a large amount of unique years) – NULL.Dude Jun 2 '17 at 18:28
  • What software are you using? Are you referring to using multiple attributes as the symbology? If so this can be done in ArcMap products under the layer's properties --> symbology --> multiple attributes. – Aggs Jul 25 '17 at 1:27

The construction year information is in so-called "wide data format", which is rather difficult to manipulate. However it is common in our daily life and most, if not all, spreadsheet software offer high functionality. An example with Excel is;

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Enter this equation in the cell F3 and copy it through.

F3: =INDEX($B$2:$E$6, 1, MATCH(MAX(B3:E3), B3:E3, 0))

After getting Year (column F) filled, join the sheet with your area layer.

Hopefully you'll get a QGIS prone answer soon; above just as a workaround.

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