Parser problem + fix

[Snaicol]

I'm trying to plot a multilayer network using Py3plex. I've created a multiedge file using this setup:

n1 l1 n2 l2 0.4
n1 l3 n3 l1 1

From the file i can assure you:

1. There are only 2 layers, called l1 and l2.
2. There are no edges between the two layers

Actually i'm using this code:

from py3plex.visualization.multilayer import *
from py3plex.core import multinet
multilayer_network = multinet.multi_layer_network().load_network("multyL.txt", directed=True, input="multiedgelist")
multilayer_network.basic_stats()
multilayer_network.visualize_network(style="diagonal")
plt.show()

This is the result:

I know that this is wrong. I've done a reverse engineering on the library to find what could be the problem. I've found it was a parse error.
Since i'm using a multi_edgelist i've analized only the method i'm using. In line 141 in ".../py3plex/core/parser.py" there is this method:

def parse_multi_edgelist(input_name,directed):
    if directed:
        G = nx.MultiDiGraph()
    else:
        G = nx.MultiGraph()
    with open(input_name) as IN:
        for line in IN:
            node_first,layer_first,node_second,layer_second,weight = line.strip().split()
            G.add_node((node_first,layer_first),type=layer_first)
            G.add_node((node_second,layer_second),type=layer_second)
            G.add_edge(node_first,node_second,weight=weight)
    return (G,None)

I've tried to rewrite this method multiples times adding a print(G.nodes(data=True) to see if I could fix it. I've notice these problems:

1. self loops: if l1 = l2_ and _n1 = n2 this code below is not working. I think there is a problem when it tries to add a second node ((node_second,layer_second),type=layer_second) since layer_first and layer_second are the same.

G.add_node((node_first,layer_first),type=layer_first)
G.add_node((node_second,layer_second),type=layer_second)
G.add_edge(node_first, node_first, weight=weight)

I think there is a problem when it tries to add a second node
((node_second,layer_second),type=layer_second) since layer_first and layer_second are the
same. In this case the code is trying to do:

G.add_node((n1,l1),type=layer_first)
G.add_node((n1, l1),type=layer_second)

Since n1 = n2 it is trying to add the same node added before with a different type even if the layers are equals.

2. If l1 = l2_ and _n1 != n2. I think the problem is always when it tries to add a second node ((node_second,layer_second),type=layer_second) since layer_first and layer_second are the same. In this case the code is trying to do:

G.add_node((n1,l1),type=layer_first)
G.add_node((n2, l1),type=layer_second)

I've modified this method to:

def parse_multi_edgelist(input_name,directed):
    if directed:
        G = nx.MultiDiGraph()
    else:
        G = nx.MultiGraph()
    with open(input_name) as IN:
        for line in IN:
            node_first,layer_first,node_second,layer_second,weight = line.strip().split()
            if layer_first == layer_second and node_first == node_second:
                # first case
                G.add_node((node_first, layer_first), type=layer_first)
            elif layer_first == layer_second and node_first != node_second:
                # second case
                G.add_node((node_first, layer_first), type=layer_first)
                G.add_node((node_second, layer_second), type=layer_first)
                G.add_edge((node_first, layer_first), (node_second, layer_second), weight=weight)
            else:
                #default case
                G.add_node((node_first, layer_first), type=layer_first)
                G.add_node((node_second, layer_second), type=layer_second)
                G.add_edge(node_first, node_second, weight=weight)
    return (G,None)

With my code i've never used the third case yet. So i don't know if there are other cases. This is the correct plot:

There is still a problem: in the first case if you add G.add_edge(node_first, node_first, weight=weight) it plots this:

This is the file i'm using.
multyL.txt

[SkBlaz]

Hello @Snaicol !

Thanks for the extensive report, I see you've more or less solved the problem yourself! I adapted a bit your code and updated the library to a newer version ('0.65), the parser should work OK now.

Your example is now part of https://github.com/SkBlaz/Py3plex/blob/master/examples/example_multilayer_visualization.py
for reproducibility.

I've also fixed the self loop problem, it seems to work fine now (case 1), please report any additional problems!

Thanks!

[SkBlaz]

If this solved the problem, you can close the issue.

Thanks!