Re: [igraph] Coordinate ranges for the output of layout algorithms

[Tamas Nepusz]

Dear Karl,

> Could you please tell me which is the coordinate range for the output
> of the layout algorithms in igraph? Is this range different for every
> layout algorithm or it remains the same for all?
The range is different for every layout algorithm, and there are no range 
limits. These coordinates are pretty much in an abstract coordinate space that 
do not relate to pixels or any other units whatsoever. In higher level 
interfaces we usually scale and shift these coordinates to screen coordinates 
before plotting a graph; i.e., the Python interface takes a Cairo drawing 
context and ensures that the graph being drawn fits exactly in the bounding box 
of the drawing context.

> Also, with yWorks yEd I like the graphs with organic layout algorithm
> applied, which I've read somewhere it is a spring-embedder type
> algorithm. Is there a similiar layout algorithm in igraph?
igraph_layout_springs is left unimplemented in the C API, that's why it is 
undocumented. We have ported the graphopt layout algorithm of Michael Schmuhl, 
which build on physical analogies: each edge is represented as a spring and 
each node is represented as an electrically charged particle. So, this 
algorithm might be close to the organic layout in yFiles, but I don't know the 
internal details of the organic layout to say this with high confidence. 
Anyway, check out igraph_layout_graphopt in the C API docs to see whether this 
is what you are looking for. More information about the algorithm can also be 
found at http://schmuhl.org/graphopt/

Best,
-- 
Tamas