Am 09.08.2015, 21:35 Uhr, schrieb Blumentrath, Stefan
<stefan.blumentr...@nina.no>:
Hi Bernd,
From your explanation it did not become quite clear to me what you
actually want to achieve.
Hi Stefan,
actually my post was a mixture between a rant and questions, cause I'm
really a bit pissed off that hard work can be destroyed that easily by
that function. When a function is missing, ok, thats life, and I'll try to
work around.
But when a function has a built-in self-detonator that will crunch my work
in a second, my blood-pressure is rising ...
The modeler really became a nice tool. The safety of the models could
maybe somehow enhanced. Already lost lots of models in the past, till I
got the idea to switch the model path to our cloud server which keeps some
versions which can be restored.
My guess is that you are struggling with a similar issue which a
colleague of mine had with the raster map calculator.
He was wondering how to use numerical variables in the raster map
calculator, which takes the formula only as a string argument (probably
it is the same with the Field calculator (I am not so familiar with this
part of QGIS)?).
The, probably not very elegant, but still simple solution is to generate
the formula in a python script in Processing, which injects your
numerical values into the formula. E.g. like this (where "F" is the
formula and "C" e.g. a (string) map variable you are going to use in the
formula):
##A=number 1
##B=number 5
##F=output string
F=str(A) + "/" + str(B) + "* C"
You can then uses this Python script in your model...
Hope that helps. It works at least well for the raster map calculator...
I'll give it a try.
Thanx for the hint
The rest of my rant was about how to "repair" a broken model, which
somehow seems to be impossible.
Cheers
Bernd
Cheers,
Stefan
-----Original Message-----
From: qgis-user-boun...@lists.osgeo.org
[mailto:qgis-user-boun...@lists.osgeo.org] On Behalf Of Bernd Vogelgesang
Sent: 9. august 2015 16:07
To: qgis-user@lists.osgeo.org
Subject: [Qgis-user] Modeler-only tools: Calculator
Hi,
In my search for a solution for the problem, that number input variables
in a model can't be referred to in the field calculator (while string
inputs, though it doesn't make any sense, can):
2 years old http://hub.qgis.org/issues/8743
http://gis.stackexchange.com/q/72569
I found the modeler-only tools Calculator, which indeed lists all
numerical inputs.
This tool doesn't come with any explanation besides: "You can refer to
model values in your formula, using single-letter variables, as follows:
a->Gridsize
and
[Enter your formula here]
Ok, so when I enter a formula there, what next????
When I put - a - there, cause I just want this value, and try to use - a
- in the field calculator, it does not work.
Furthermore: The formula has disappeared after reopening the function:
http://hub.qgis.org/issues/11434#note-9
It does not seem to be usable at all.
And it destroyed my three-days work on a model, cause by mistake I
entered nothing and hit ok and saved the thing, which caused a python
error and the model can't be opend again.
Only the fact that I work on a cloud where I can restore my last version
from yesterday has saved my ass. (Working locally, the hole work
would have been gone forever!).
There seems to be no way to get rid of that function from the model
manually in a text editor, identifying the section and removing it still
leaves a crippled model which refuses to load.
Questions:
Is there anyone around who is able to explain me the structure of a
model file or point to least some minimal documentation?. Why do nearly
every manual operations on a model in an editor destroy them, and how
can I avoid this?
Does anyone know how to use this Calculator without destroying the model?
Is there any workaround for referencing numerical input in the field
calculator.
Cheers
Bernd
QGIS2.8.3, Linux Mint 17
--
Bernd Vogelgesang
Siedlerstraße 2
91083 Baiersdorf/Igelsdorf
Tel: 09133-825374
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--
Bernd Vogelgesang
Siedlerstraße 2
91083 Baiersdorf/Igelsdorf
Tel: 09133-825374
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