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I have a large postcode dataset of ~1.6 million observations in Layer A.

I have a smaller dataset of ~5000 observations in Layer B.

Layer A contains an ID that matches postcodes with observations in Layer B.

I want to find the distance between every observation in Layer A, and the associated observation in Layer B, using the common ID field.

Note, I do not want to do Nearest Neighbor Analysis, there is a specific network structure.

  • So does each point in Layer A have a unique ID? And points in Layer B have a matching ID? Do multiple points in the same layer have the same ID? – Joseph Mar 15 '17 at 12:54
  • Each point in Layer A has a unique ID (a postcode), and then an ID that matches the observations in Layer B. There shouldn't be multiple points in the same layer with the same ID. – Thirst for Knowledge Mar 16 '17 at 7:25
  • Although the solution I posted deals with a fraction of points you have, perhaps you could consider using PostGIS for this? In which case, I'll happily delete my post as I don't think it will work well for that huge a dataset :) – Joseph Mar 17 '17 at 10:34
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I would probably do the following:

  1. Copy/paste your 5000 points from Layer B into Layer A (or run a merge tool).
  2. Install the Points2One plugin from:

    Plugins > Manage and Install Plugins...
    
  3. Run this plugin on your merged layer.


Example:

  1. A sample point layer created from two separate layers (both with a common ID field) where I merged them:

    Sample point layer

  2. Then run the Points2One plugin selected the relevant options:

    Points2One plugin interface

  3. Output line shapefile should contain lines for each unique postcode:

    Output line shapefile

  4. Use the Field Calculator on the output to create a new field containing the distance values using the expression $length:

    Final result

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Is Virtual Layer an option?

From menu Layer | Add Layer | Add/Edit Virtual layer.

enter image description here

Query:

SELECT LayerA.postcodes AS Postcodes, 
       st_distance(LayerA.geometry, LayerB.geometry) AS Distance
FROM   LayerA INNER JOIN LayerB
ON     LayerA.postcodes = LayerB.postcodes

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