[Qgis-user] How to concatenate strings inside r.mapcalculator formula text box?

[Yasser Said Lopez de Olmos Reyes]

Hello all!

I'm a professor at the Metropolitan Autonomous University in Mexico. We are
trying to integrate FOSS software while teaching GIS and we started with
QGIS 1.8 release. We are developing an academic course with QGIS 2.x and
one of the modules is how to use the graphical modeler in QGIS 2.x.

While designing a model we encountered difficult to use a custom formula
inside raster calculator (r.mapcalculator, exactly). Is there a way to ask
for a number (as a number or as a string) at execution to multiply it for a
raster layer if this number is not in the formula textbox?

Something like:
1. Give me a number
2. Give me a raster
3. Multiply given number (1) by a raster (2).


The user of the model shouldn't need to know how to write the formula. I've
been thinking we can somehow concatenate strings inside r.mapcalculator's
formula textbox, but can't make it work. Any suggestions will be highly
appreciated.

PS. Python scripting is not an option at this course level.


-- 
Saludos,

Yasser
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