1

When incorporating the field calculator into the graphical modeler in QGIS is it possible to update an existing field without having to create a new field and then remove the existing.

For example I have a field called "MEAN" and lets say we have one record with a value of 100. Is it possible to update that field with the following simple sum "MEAN" / 10. I know this is possible outside of the modeler environment by using the "Update existing field" tick box but I can't seem to replicate this in the modeler enter image description here

AWGIS
  • 3,220
  • 1
  • 21
  • 36

1 Answers1

3

You can do this by just setting the input field to an already existing one. You can either type it by hand or use a model input:

enter image description here

or

enter image description here

Here is an alternative, I personally prefer: Use "refactor fields" instead of "field calculator". This tool has some advantages:

  • You can use input-variables in your expression (in field calculator you can not choose them from the expression list, and if you enter them manually, they often fail to work)
  • You can add several calculations at once
  • You can also change the fieldname and fieldtype if you want to

Only disadvantage is, that fields not listed here will be dropped. So if you have a huge list or variing fields, its better to stick with field calculator.

enter image description here

*in my example im using "id" as field instead of "mean"

MrXsquared
  • 34,292
  • 21
  • 67
  • 117