[Qgis-developer] Raster calc syntax

[Nathan Woodrow]

>
> Alternatively, how about categorising operators like the expression
> builder in a spreadsheet?


Have you seen the expression builder used for labeling?
http://woostuff.wordpress.com/2011/10/27/expression-based-labeling/

The goal is to replace the current calculator with something that.

Something else that might be useful is a preview window for the raster


This would be a cool idea.

- Nathan

On Thu, Jan 26, 2012 at 9:06 PM, John Donovan <mersey.viking at gmail.com>wrote:

> One way of hiding some of the syntactic complexity might be to use one
> of the visual workflow systems like Orange http://orange.biolab.si/ to
> construct raster operations, especially if it somehow tied in with the
> SAGA/Grass/etc. workflow stuff that's being developed. True, this is
> not an insignificant amount of work, but if all it did was generate
> valid rastercalc expressions, then it can sit on top of the current
> system rather than replace it.
>
> Alternatively, how about categorising operators like the expression
> builder in a spreadsheet?
>
> Something else that might be useful is a preview window for the raster
> calculator. I got bitten by a similar issue to Tim, where I wanted to
> invert the values in my raster. I used:
> -myraster at 1
> Which is a valid expression, but returned 0 for all values. Instead I
> had to use:
> -(myraster at 1)
>
> This wasted 20 minutes on my very large dataset. In hindsight I should
> have done in the first place what I did in the end, and tested it with
> a subset of my big raster, but a small thumbnail like some of the Gimp
> plug-ins have would have saved me some time.
>
> -John
>
> On 26 January 2012 10:43, Marco Hugentobler
> <marco.hugentobler at sourcepole.ch> wrote:
> > Hi Nathan
> >
> >
> >>One question, how needed is the Min X, Max Y etc stuff.  Currently it
> takes
> >> up a lot of room and clutters (IMO) the interface.  I was thinking we
> might
> >> be able to hide it in an >advanced section if it is only used rarely.
> >
> > IMO, you could move those element into an advanced section. It is
> important
> > to have the possibility to set the output resolution, but not a setting
> you
> > need fast access to.
> >
> > Regards,
> > Marco
> >
> >
> > On 26.01.2012 01:15, Nathan Woodrow wrote:
> >
> > Hey Paolo,
> >
> > I stated working on adding the expression builder widget last night,
> didn't
> > get very far as I had to do some other things.
> >
> > One question, how needed is the Min X, Max Y etc stuff.  Currently it
> takes
> > up a lot of room and clutters (IMO) the interface.  I was thinking we
> might
> > be able to hide it in an advanced section if it is only used rarely.
> >
> > - Nathan
> >
> > On Thu, Jan 26, 2012 at 4:13 AM, Paolo Cavallini <cavallini at faunalia.it>
> > wrote:
> >>
> >> Hi all.
> >> How about simplifying the syntax of raster calc? If even Tim can get
> >> wrong:
> >>
> >>
> http://linfiniti.com/2012/01/simple-binary-raster-reclassification-in-qgis/
> >> this means that the average user will be in trouble.
> >> Am I wrong?
> >> Of course, using the expression widget now used for field calc and for
> >> labelling
> >> would probably solve the issue.
> >> All the best.
> >> --
> >> Paolo Cavallini - Faunalia
> >> www.faunalia.eu
> >> Full contact details at www.faunalia.eu/pc
> >> _______________________________________________
> >> Qgis-developer mailing list
> >> Qgis-developer at lists.osgeo.org
> >> http://lists.osgeo.org/mailman/listinfo/qgis-developer
> >
> >
> >
> >
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> >
> >
> > --
> > Dr. Marco Hugentobler
> > Sourcepole -  Linux & Open Source Solutions
> > Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
> > marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
> > Technical Advisor QGIS Project Steering Committee
> >
> >
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> >
>
>
>
> --
> One of the advantages of being disorderly is that one is constantly
> making exciting discoveries. - AA Milne
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