Even though I found similar questions, I couldn't find a suitable answer for the problem I have.

I want to create a model that calculates the difference between two fields ("NUMPOINTS") from different vector files and populate a new field with the result in a new vector file.

My input are 2 vector layers: 'Events A' and 'Events B'. These tables have the same fields, including a common "id" field.

I need to create a 'Table C' where "DIFFERENCE" field is calculated as follow: "NUMPOINTS" ('Table B') - "NUMPOINTS" ('Table A')

So far, I managed to create a Join, but I don't know how to create a new field with input from the two input files.

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1 Answer 1


you can use the fieldcalculator in your model to do the calculation:

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since your fields have the same name "NUMPOINTS" you can use a prefix for the joind NUMPOINTS field in the JOIN operation:

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the formula in the fieldcalculator would be:

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  • It worked, thanks a lot! Aug 26, 2023 at 13:26
  • if this answer is a solution to your question you can mark the answer as accepted...
    – eurojam
    Aug 27, 2023 at 9:08

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