[Qgis-user] Qgis 3.6 network analysis

[Nicolas Cadieux]

Hi Bernd,

R is one of those softwares I need to relearn every second year!! I just don’t use it enough but the package look promising.  Did you create that particular package?

Nicolas

> Le 16 avr. 2019 à 09:43, Bernd Vogelgesang <bernd.vogelgesang at gmx.de> a écrit :
> 
> Hi Nicolas,
> 
> I'm neither familiar with networks nor rivers nor python, but i made
> myself befriended with R in the last years. I never used it from inside
> QGIS but "standalone" with R studio.
> 
> As it's a real data-cruncher and easy to debug the code line by line, I
> use R for all "more complex" situations where you have to find your way
> by trial-and-error to the final solution.
> 
> I can just recommend to have a look at this
> https://cran.r-project.org/web/packages/riverdist/vignettes/riverdist_vignette.html
> page, as it looks quite promising to what you want to achieve (from
> quick read)
> 
> In case you are interested in trying that route, just contact me in case
> of questions / assistance etc.
> 
> Cheers,
> Bernd
> 
>> Am 16.04.19 um 06:13 schrieb Nicolas Cadieux:
>> Hi again,
>> 
>> Thanks Nyall, Micha and Alessandro for your help on correcting the
>> river flow directions.  I am still working on it but you gave me the
>> right tools.  The next step of my project will be to use my river flow
>> network and find the shortest path between THOUSANDS of points (so I
>> will need to batch it or script it in Python).
>> 
>> It gets complicated as I will need to calculate the total trip for
>> each shortest path (easy) and then the percentage of that trip that
>> was made going downstream (the rest being the upstream trip).  I don't
>> know if there is a tool for that?  If not, my goal was to use the
>> shortest path lines to do a spatial query on my network and figure
>> things from there.
>> 
>> Anyways, I don't have much experience with networks so that's what I
>> need to figure out.  I also mostly use Python outside of QGIS so my
>> questions are basic for now.  I see that many plugins have been
>> incorporated in Processing but the Shortest path (point to point)
>> builds a new graph every time.  I figure I need to build a graph but
>> that does not seem to be available in QGIS 3.6.
>> 
>> I found this
>> https://docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/network_analysis.html#building-a-graph
>> but the very first command "from qgis.networkanalysis import *" in the
>> QGIS python console  indicates "ModuleNotFoundError: No module named
>> 'qgis.networkanalysis'".
>> 
>> Question 1: Is the qgis.networkanalysis module being replaced or
>> renamed in QGIS 3.6 (OSGEO4w64 intall