[SoC] Weekly report #3 - GRASS Interactive Scatter Plot Tool

Štěpán Turek stepan.turek at seznam.cz
Sat Jul 6 07:19:39 PDT 2013

Hi Hamish and Michael,

your questions are connected I will try to explain both.

The scatter plot tool backend is run in same process as wxGUI. If you select
some area in scatter plot, then data from numpy arrays are passed to the 
backend (through ctypes), which describes selected areas in scatters plots. 
And the backend computes corresponding areas which will be highlighted in 
all opened scatter plots. To avoid frozing of the wxGUI, the computation is 
done in separate python thread. 

Currently r.out.bin is used to bypass inability to set region in raster 
library for different rasters. When user choose raster group for analysis in
the tool, it is exported into binary files in current region and the backend
works directly with the binary files. This is not very nice. 

If the backend would be written as module, then I would need to create 
temporary files to pass the selected areas, which does not seem very elegant
to me. 

In simplified way the idea is that the library should give you option 
whether you want to open and then work with raster file according to the 
statically set variables (in structure R__) or open it with dynamically 
defined variables. 

It could be also useful for Pietro's pyGRASS API. And it would be first 
small step to achieve compilation of raster modules as library instead of 
different programs. I am working on more concrete proposal of the changes in
raster library during this weekend. 

I am new to this problematic, so all these suggestions can be totally 



---------- Původní zpráva ----------
Od: Michael Barton <Michael.Barton at asu.edu>
Datum: 6. 7. 2013
Předmět: Re: [SoC] Weekly report #3 - GRASS Interactive Scatter Plot Tool

"So I take it you are not using r.stats to generate the data to plot, but 
are getting data directly accessing rasters via GRASS libraries?



I am interested to hear more about the library limitations.. you
mean the WIND region, right? I'd be surprised if WIND_OVERRIDE or
GRASS_REGION enviro variables (and the python wrappers for them)
didn't provide full control for whatever someone might like to do.

I would guess if the scatter tool was spawned as an independent
process, it could maintain its own environment & so it's own region
override enviro variables. or simply unset the wxGUI display overrides
and just use the mapset's real computational region read directly from
the WIND file?


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