[Qgis-user] Qgis 3.6 network analysis

[Bernd Vogelgesang]

Hi Nicolas,

The R-Ecosystem is definately worth to be relearned. Especially with
introduction of simple features, the sf-package, in combination with the
tidyverse, vector and data handling in R became much easier. My once
hundreds of lines of code condensed to some dozends.

And no, I have nothing to do with that package, I just stumbled upon it
after reading about your case and a quick search for tools in R for such
a use case.

Good luck,

Bernd

Am 16.04.19 um 15:54 schrieb 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