Changing labels of a graph and access edge thickness

graph

asked 2021-01-05 12:27:03 +0200

Cyrille
1413 ●24 ●70 ●129

updated 2021-01-05 16:14:19 +0200

slelievre
17654 ●22 ●160 ●348 http://carva.org/samue...

This is a graph. But now I want the vertices labeled with {'A', 'B', 'C'} or some names, and colored. And I have not seen an option for specifying the thickness of edges and of the arrow head.

Working with this example adapted from the documentation:

D = DiGraph({0: [0, 1], 1: [2], 2: [3]}, loops=True)
D.show(edge_colors={(0, 1, 1): [(0, 1), (2, 3)]})

I have been surprised not to be allowed to put edge_colors inside show() in my case, but this is of less importance since there is another way.

Of more importance, in graph options I have not seen any command for the thickness of the edges and of the arrow head.

One more time thanks for your help.

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answered 2021-01-05 12:51:49 +0200

tmonteil
27323 ●31 ●202 ●514 http://wiki.sagemath.o...

updated 2021-01-05 12:59:27 +0200

You can relabel the graph with the relabel method:

sage: D.relabel(['A','B','C','D'])

check

sage: D.relabel?

for more options.

Regarding coloring the vertices, you can do

sage: D.show(vertex_colors={'blue':[0,2],'green':[1],'black':[3]})

see

sage: D.plot?

for more plotting options.

There might be one somewhere, but i do not see an edge-thickness option either in the documentation. However, looking into the source code of the GraphPlot class:

sage: from sage.graphs.graph_plot import GraphPlot
sage: GraphPlot??

It seems that you can do:

sage: D.show(edge_thickness=4)

Also, there is a edge_style option which can be one of 'solid', 'dashed', 'dotted', dashdot', 'None'.

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Comments

Thanks. But D.relabel() generates an error in my case. Also ?relabel() gives "Object relabel() not found."

Cyrille ( 2021-01-05 13:26:17 +0200 )edit

Which version of sagemath are you using and what's the error message ?

sage: D = DiGraph({0:[0,1], 1:[2], 2:[3]}, loops=True)                                                                                              
sage: D.relabel(['A','B','C','D'])                                                                                                                  
sage: D.edges(labels=False)                                                                                                                         
[('A', 'A'), ('A', 'B'), ('B', 'C'), ('C', 'D')]

David Coudert ( 2021-01-05 13:32:37 +0200 )edit

Sorry but this

D = DiGraph( { 0: [1, 2, 3, 4], 1: [2, 3, 4], 2: [3, 4], 3: [4], 4:[]})
D.relabel(['A','B','C','D'])
vc = {'#51c8f1':[0,1,2,3,4]}
ec = {'#ad8393':[(0,1),(0,4)],'#4c75a3':[(2,4),(3,4)]}
D.edges(labels=False)

generates this

<repr(<sage.graphs.views.EdgesView at 0x6ffec68c7110>) failed: TypeError: '<' not supported between instances of 'int' and 'str'>

Cyrille ( 2021-01-05 14:32:26 +0200 )edit

My version is sage 9.2

Cyrille ( 2021-01-05 16:48:27 +0200 )edit

Because the vertices of your new graph are 'A', 'B', 'C', 'D', 4 and since 'A' and 4 are not comparable (a string vs an integer), apparently, you need to add sort=False option to prevent sorting :

sage: D.edges(labels=False, sort=False)
[('A', 'B'), ('A', 'C'), ('A', 'D'), ('A', 4), ('B', 'C'), ('B', 'D'), ('B', 4), ('C', 'D'), ('C', 4), ('D', 4)]

I would say that raising an error in such case is a kind of bug.