[Qgis-user] Model designer: Using value from a Number input as a parameter in a Raster Calculator expression

[Martin Weis]

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 at 1" * parameter('my_number')/ 
> or /"A at 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 at 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 at 1" * 
> parameter('my_number')/
> 
> So, how do i declare and use a Number Input inside a raster calculator 
> expression ??
> 
> 
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