Re: [igraph] Different plotting of graphs in R and in Python

[Charles Novaes de Santana]

Just found that the function graph.union does the "sum" I want to do. But, again, I only can run this function correctly in R, not in Python.

Given the code in R:

library(igraph)
nodes1 = c("a","b","c")
nodes2 = c("c","d","e")
edges1 = matrix( c("a", "b", "b", "c","c","a"), nc = 2, byrow = TRUE)
edges2 = matrix( c("c", "d", "d", "e","e","c"), nc = 2, byrow = TRUE)
g1 = graph(edges1,directed=FALSE)
g2 = graph(edges2,directed=FALSE)

g3 = graph.union(g1,g2);

plot(g3);

Now the equivalent code in Python:

import igraph
nodes1 = ["a","b","c"]
nodes2 = ["c","d","e"]
edges1 = [["a","b"],["b","c"],["c","a"]]
edges2 = [["c","d"],["d","e"],["e","c"]]
g1 = igraph.Graph(directed=False)
g2 = igraph.Graph(directed=False)
g1.add_vertices(nodes1)
g2.add_vertices(nodes2)
g1.add_edges(edges1)
g2.add_edges(edges2)

g3 = igraph.Graph.union(g1,g2)

plot(g3)

As you can see, the behaviour of the plot in Python is still different from the one in R. Actually, it is worst than the one I had before, because now I only can see 3 vertices. What am I missing here?

Thanks again for any tip,

Best,

Charles

On 21 September 2015 at 23:16, Charles Novaes de Santana <address@hidden> wrote:

Dear all,

I am trying to plot a "sum of graphs" in R and in Python, using Igraph. I can do it correctly in R, but I am facing some problems to reproduce it in Python. I was wondering if you could help me with this.

Please consider the following toy code in R:

library(igraph)
nodes1 = c("a","b","c")
nodes2 = c("c","d","e")
edges1 = matrix( c("a", "b", "b", "c","c","a"), nc = 2, byrow = TRUE)
edges2 = matrix( c("c", "d", "d", "e","e","c"), nc = 2, byrow = TRUE)
g1 = graph(edges1,directed=FALSE)
g2 = graph(edges2,directed=FALSE)

plot(g1+g2);

you can see that in the plot(g1+g2) the vertex "c" is shared by both graphs. So actually I can plot one connected graph with the vertices "a","b","c","d","e".

I would like to reproduce it in Python. The best way I think now is the following code, but it is failing:

import igraph
nodes1 = ["a","b","c"]
nodes2 = ["c","d","e"]
edges1 = [["a","b"],["b","c"],["c","a"]]
edges2 = [["c","d"],["d","e"],["e","c"]]
g1 = igraph.Graph(directed=False)
g2 = igraph.Graph(directed=False)
g1.add_vertices(nodes1)
g2.add_vertices(nodes2)
g1.add_edges(edges1)
g2.add_edges(edges2)

igraph.plot(g1+g2);

you can see that the igraph.plot(g1+g2) does not consider that vertex "c" is shared by g1 and g2. Do you have any idea why these codes have different behaviour? I know I am building the graphs in different ways, but I was not able to build the graph in Python in the same way I do it in R.

Sorry if it is a silly question (I used to program in R during some years, but I am just a beginner in Python). Thanks for any help or advice!

Best,

Charles

--

Um axé! :)

--
Charles Novaes de Santana, PhD
http://www.imedea.uib-csic.es/~charles

--

Um axé! :)

--
Charles Novaes de Santana, PhD
http://www.imedea.uib-csic.es/~charles