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I try to do a simple model with the Model Designer of QGIS and I have an issue with the algorithms Select by expression.

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And when I want to check the validity of the model the explanation is just : The Algorithm is not available

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You can see the settings I used for Select by expression

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Does someone know why I can't use Select by expression ?

Moreover, you can see my QGIS settings with the following screenshot

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OK, as Babel said I tried to use Extract selected features and it works but only if I set a model output also for this algorithm enter image description here

When I set algorithm output it doesn't work

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  • Hi Sof, welchome to GIS SE. Great to have you here. I think we need a bit more information - so you were - obviously - able to select the algorithm Select by expression. Can you show us the settings? What QGIS version do you use? What happens when you try to delete and add again the algorithm?
    – Babel
    Commented Jun 9, 2023 at 14:49
  • Hello Babel, I use the 3.22.4 version of QGIS (Białowieża) on a Ubuntu laptop 22.04.2 LTS. When I try to delete and again the algorithm it doesn't change : the model is still invalid
    – Sof
    Commented Jun 9, 2023 at 14:55
  • Which settings did you make in the Select by expression algorithm? Please show a screenshot of this
    – Babel
    Commented Jun 9, 2023 at 14:58
  • I have just done it. Do you think the expression is the cause of the problem ?
    – Sof
    Commented Jun 9, 2023 at 15:03
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    As I said above it works with Extract selected features (when I set Model output and not when I set Algorithm output). Thank you Babel
    – Sof
    Commented Jun 9, 2023 at 16:42

1 Answer 1

Reset to default
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You have not set any valid input for Modify current selection by, it is empty. If you want to create a new selection, set the icon to the left to Value (icon 123 instead of the gear icon) and choose an option, e.g. creating new selection.

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Use an Extract selected Features algorithm after the Select by expression algorithm, then use this as input for Clip algorithm.

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  • When I do that, it is strange. The model is valid and I can run it. But when I run it the selection by expression was not done. Only the clip was done
    – Sof
    Commented Jun 9, 2023 at 15:19
  • So you should post the Clip settings as well. Or try to use a Extract selected Features algorithm after the Select by expression algorithm, then use this as input for Clip.
    – Babel
    Commented Jun 9, 2023 at 15:21
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    As I say above I confirmed it works (with Model output). Thank you Babel
    – Sof
    Commented Jun 9, 2023 at 16:40

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