[Qgis-user] R: Reclassify field values from txt rule file in QGIS

[fabio castelli]

Hi Andrea,

thank you very much for your support. Sorry, I'm new at this.
I've tried to print the code that you sent me in the Python console but I get errors:

[cid:785caf1b-9058-4177-9b65-b858278771ed]

I'm pretty sure I miss some basics here, could you please kindly explain the procedure?

Fabio


________________________________
Da: QGIS-User <qgis-user-bounces at lists.osgeo.org> per conto di Andrea Giudiceandrea via QGIS-User <qgis-user at lists.osgeo.org>
Inviato: giovedì 29 giugno 2023 08:24
A: qgis-user at lists.osgeo.org <qgis-user at lists.osgeo.org>
Oggetto: Re: [Qgis-user] Reclassify field values from txt rule file in QGIS

> fabio castelli fabio.castelli92 at outlook.it
> Wed Jun 28 05:52:45 PDT 2023

> I kindly ask for your support with an issue related to the reclassification of attribute tables with the v.reclass function.
> Here's the link to the question posted on Stackexchenge: https://gis.stackexchange.com/questions/462318/reclassify-field-values-from-txt-rule-file-in-qgis

Hi Fabio,
looking at your question posted on Stackexchenge, the error message
("Either 'rules' or 'column' must be specified") is very clear and it is
due to the fact the you have specified both the "rules" and "column"
parameters instead of only one of them.

Anyway, it looks like it is actually incorrectly impossible to specify
only the "rules" parameter in the QGIS processing algorithm GUI for the
v.reclass GRASS-GIS module without also specifying the "column"
parameter: this is due to the fact that the "column" parameter is
incorrectly flagged as mandatory instead of optional.

You can workaround this issue editing the v.reclass.txt file in the
folder with path [QGIS installation
dir]\apps\qgis\python\plugins\grassprovider\description\ or [QGIS
installation
dir]\apps\qgis-ltr\python\plugins\grassprovider\description\ (provided
you are using QGIS 3.32 or QGIS LTR 3.28 on Windows) and to change the
the sixth line from:

QgsProcessingParameterField|column|The name of the column whose values
are to be used as new categories|None|input|-1|False|False

to:

QgsProcessingParameterField|column|The name of the column whose values
are to be used as new categories|None|input|-1|False|True


I also suggest you to read the v.reclass GRASS-GIS module manual
available at https://grass.osgeo.org/grass82/manuals/v.reclass.html in
order to better understand what the "rules" file must contains.


Best regards.

Andrea Giudiceandrea
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