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In QGIS is there a way to assign ascending numbers (attribute) to polygons that are located in a row. The polygons were not created in sequential order.

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    I don't think there's a tool to do it. The approach would be to build the adjacency graph of the polygons then starting from one end compute the distance to all the other nodes in the graph. I can't find a plugin to compute the adjacency network as a line coverage (although I think my old topocolor plugin did it) which would be the first step. Requires some python coding. Check the "Map Colouring" plugin's code for ideas on computing adjacency graphs...
    – Spacedman
    Jul 7, 2016 at 15:53
  • If the data was in PostgreSQL, then you could use this solution
    – Vince
    Jul 8, 2016 at 0:25
  • @Vince that might work assuming the connected polygons are aligned east-west. The map image above looks like a row of plots on a street, which could be going in any direction, or even on a curve. Dion, Is that true? Are you trying to number plots on a street?
    – Spacedman
    Jul 8, 2016 at 6:47
  • @Spacedman yes that is correct. I am trying to assign numbers to plots on a street. Would it help if I generated polygon centroids, connect the points with a line and then determine the sequence of the points along the line?
    – Dion
    Jul 8, 2016 at 8:46
  • @Dion that's sort of what I mean about building an adjacency graph. You'd still need some python code to "walk the line" and work out the corresponding numbers.
    – Spacedman
    Jul 8, 2016 at 10:38

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Once you have the polygon centroids you could get the coordinates of the centroid and then sort them (e.g. by west to east coordinate) to get the correct order.

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