Hi,
You could consider https://networkx.org/ if you are really looking for
just a graph. It's a pure Python library but it's not included with
QGIS. It's not too difficult to learn but geared towards analysis and
not visualization like Graphviz. (I have never user Graphviz so don't
take my word for it.)
You can still do what you want in QGIS. Shapefile lines could
simplified by changing the geometry into a simple line between the first
and last node. Qgis has the advantage (and disadvantage if the network
is complicated) of giving you complete control on were you position
nodes on a map. Graph libraries usually give you a choice of rendering
styles but it gets complicated if you want complete control on the
rendering. You could also use QGIS to draw the shapefile and export
those to Graphviz for visualization. You could also look at Cytoscape
and Gephi that seem to be vizualisation software for graphs.
https://gephi.org/
https://cytoscape.org/
Nicolas
On 2021-02-10 11:39 a.m., chris hermansen wrote:
Giacomo and list,
On Wed, Feb 10, 2021 at 4:05 AM Giacomo Uguccioni
<[email protected] <mailto:[email protected]>> wrote:
Thanks a lot!
I would like to represent a shapefile or more shapefiles of nodes
and connections (lines and points)
in a layout similar to an electrical scheme, a symbolic and
conceptual scheme and not a geographical one.
I attached an image with qgis view and output that I would like to
get.
In your graph representation (version to the right in your sketch) how
do you determine that A is the start node? (and not 3 or 4?)
This kind of diagram is what Graphviz is built to represent. You will
need to convert your shapefiles to a Graphviz input program. A
reasonable starting approach might be to use some vector operations to
get attribute tables that look like [from-node,to-node] along with the
node attributes. I suggest you study the Graphviz documentation,
which is quite excellent and full of worked examples, to see how to
draw the sketch you presented here, and then revisit your shapefiles
to think about how to convert them to that format.
--
Chris Hermansen · clhermansen "at" gmail "dot" com
C'est ma façon de parler.
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Nicolas Cadieux
https://gitlab.com/njacadieux
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