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I am trying to get a certain expression in QGIS right, but because I am quite new to QGIS expressions, I cannot quite get it right.

Basically I want another field, to have specific kind of text based on the value of the pre-existing field. In this case, when the height of a tree ("Height" field) has the following values, the following text will be displayed:

  • <6 meters: >6 meters 3rd category
  • between 6-12 meters: 2nd category
  • >12 meters: 1st category

How exactly do I do this and what I am doing wrong here?

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As for a side note, should I better do this using AutoFields plugin, so I am sure it happens automatically?

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  • Regarding your last question, definitely! Use AutoFields to get the 'category' field up-to-date (e.g., when you insert or modify heights). Just use the expression given by @armoraer in the AutoFields dialog.
    – Germán Carrillo
    Mar 20, 2017 at 16:07

1 Answer 1

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You can use a CASE expression:

CASE
  WHEN "Hoogte" <= 6 THEN '6 meter, 3rde categorie'
  WHEN "Hoogte" >= 6 AND "Hoogte" <= 12 THEN '6-12 meter, 2de categorie'
  ELSE '12 meter, 1ste categorie'
END

I'm not sure what you mean by "autofields" though?

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  • Beat me to it, good answer. To note, the "Hoogte" field must be numeric for this to work. The autofields, might refer to virtual fields, which can generate a field automatically based on this query. But probably best left for another question.
    – HeikkiVesanto
    Mar 20, 2017 at 15:55
  • AutoFields is a QGIS plugin that updates field values based on expressions. It writes the updated values directly in the source data.
    – Germán Carrillo
    Mar 20, 2017 at 16:03

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