Thanks Martin, for the heads-up.
In hindsight, the Model Designer of course needs a "pre-calculate"
feature like this to incorporate external programs and function
libraries ( that is not capable of directly read and evaluate a QGIS
internal variable or expression).
Med venlig hilsen / Best regards
Bo Victor Thomsen
On 28/05/2025 20.05, Martin Weis via QGIS-User wrote:
Hello,
Try pre-calculated formula:
'A* ' || @number
see the model in this gist:
https://gist.github.com/Marwe/32c41f69e99782b023c34b913b507470
Worked for me :)
Have fun
Martin
Am 27.05.25 um 11:02 schrieb Bo Victor Thomsen via QGIS-User:
Hi list -
I can't find a method to use a Number input as a part of raster
calculator expression in Model Designer.
Using QGIS version 3.42, in Model Designer I've:
* Defined a Number Input field: /my_number/
* Defined a Raster Layer selector : /my_raster/
* Defined a Rater Calculator algorithm: /multiplication/
Now the crucial question: How to use the number from my number input
in an expression inside Raster Calculator?
Ex. for a simple multiplication: /"A@1" * parameter('my_number')/ or
/"A@1" * @my_number/
Whatever I do, I get an error message like this:
Algorithm 'model' starting…
Input parameters:
{ 'my_number' : 22, 'my_raster' : 'D:/gis/gis_analyser/flis_volumen/
normaliseret.tif', 'resultat' : 'TEMPORARY_OUTPUT' }
Prepare algorithm: native:modelerrastercalc_1
Running multiplication [1/1]
Input Parameters:
{ CELL_SIZE: None, CREATION_OPTIONS: None, CRS: None, EXPRESSION:
'"A@1" * parameter(\'my_number\')', EXTENT: None, LAYERS: ['D:/gis/
gis_analyser/flis_volumen/normaliseret.tif'], OUTPUT:
'TEMPORARY_OUTPUT' }
Error encountered while running multiplication: Error parsing formula.
Execution failed after 0.04 seconds
The error message indicate an error in my expression: /"A@1" *
parameter('my_number')/
So, how do i declare and use a Number Input inside a raster
calculator expression ??
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