how to draw directed graphs using networkx in python

Question

I have some nodes coming from a script that I want to map on to a graph  In the below  I want to use Arrow to go from A to D and probably have the edge colored too in  red or something    This is basically  like a path from A to D when all other nodes are present  you can imagine each nodes as cities and traveling from A to D requires directions  with arrow heads    This code below builds the graph  import networkx as nx import numpy as np import matplotlib pyplot as plt  G   nx Graph   G add edges from         A    B      A    C      D    B      E    C      E    F           B    H      B    G      B    F      C    G      val map     A   1 0              D   0 5714285714285714              H   0 0   values    val map get node  0 25  for node in G nodes     nx draw G  cmap   plt get cmap  jet    node color   values  plt show     but I want something like shown in the image    Arrow heads of the first image and the edges in red color onto the second image

User · Answer

import networkx as nx import matplotlib pyplot as plt  G   nx DiGraph   G add node  quot A quot   G add node  quot B quot   G add node  quot C quot   G add node  quot D quot   G add node  quot E quot   G add node  quot F quot   G add node  quot G quot   G add edge  quot A quot   quot B quot   G add edge  quot B quot   quot C quot   G add edge  quot C quot   quot E quot   G add edge  quot C quot   quot F quot   G add edge  quot D quot   quot E quot   G add edge  quot F quot   quot G quot    print G nodes    print G edges     pos   nx spring layout G   nx draw networkx nodes G  pos  nx draw networkx labels G  pos  nx draw networkx edges G  pos  edge color  r   arrows   True   plt show

User · Answer

import networkx as nx import matplotlib pyplot as plt  g   nx DiGraph   g add nodes from  1 2 3 4 5   g add edge 1 2  g add edge 4 2  g add edge 3 5  g add edge 2 3  g add edge 5 4   nx draw g with labels True  plt draw   plt show     This is just simple how to draw directed graph using python 3 x using networkx  just simple representation and can be modified and colored etc  See the generated graph here   Note  It s just a simple representation  Weighted Edges could be added like  g add edges from   1 2   2 5    weight 2    and hence plotted again

User · Answer

I only put this in for completeness   I ve learned plenty from marius and mdml   Here are the edge weights   Sorry about the arrows   Looks like I m not the only one saying it can t be helped   I couldn t render this with ipython notebook I had to go straight from python which was the problem with getting my edge weights in sooner    import networkx as nx import numpy as np import matplotlib pyplot as plt import pylab  G   nx DiGraph    G add edges from    A    B     C   D     G   D     weight 1  G add edges from    D   A     D   E     B   D     D   E     weight 2  G add edges from    B   C     E   F     weight 3  G add edges from    C   F     weight 4    val map     A   1 0                      D   0 5714285714285714                                 H   0 0   values    val map get node  0 45  for node in G nodes    edge labels dict    u v   d  weight                     for u v d in G edges data True    red edges      C   D     D   A    edge colors     black  if not edge in red edges else  red  for edge in G edges     pos nx spring layout G  nx draw networkx edge labels G pos edge labels edge labels  nx draw G pos  node color   values  node size 1500 edge color edge colors edge cmap plt cm Reds  pylab show

User · Answer

Fully fleshed out example with arrows for only the red edges   import networkx as nx import matplotlib pyplot as plt  G   nx DiGraph   G add edges from         A    B      A    C      D    B      E    C      E    F           B    H      B    G      B    F      C    G      val map     A   1 0              D   0 5714285714285714              H   0 0   values    val map get node  0 25  for node in G nodes       Specify the edges you want here red edges      A    C      E    C    edge colours     black  if not edge in red edges else  red                  for edge in G edges    black edges    edge for edge in G edges   if edge not in red edges     Need to create a layout when doing   separate calls to draw nodes and edges pos   nx spring layout G  nx draw networkx nodes G  pos  cmap plt get cmap  jet                            node color   values  node size   500  nx draw networkx labels G  pos  nx draw networkx edges G  pos  edgelist red edges  edge color  r   arrows True  nx draw networkx edges G  pos  edgelist black edges  arrows False  plt show

User · Answer

Instead of regular nx draw you may want to use  nx draw networkx G   pos  arrows  with labels    For example  nx draw networkx G  arrows True    options   You can add options by initialising that    variable like this  options          node color    blue        node size   100       width   3       arrowstyle    -  gt         arrowsize   12     Also some functions support the directed True parameter In this case this state is the default one  G   nx DiGraph directed True   The networkx reference is found here

User · Answer

You need to use a directed graph instead of a graph  i e   G   nx DiGraph     Then  create a list of the edge colors you want to use and pass those to nx draw  as shown by  Marius    Putting this all together  I get the image below  Still not quite the other picture you show  I don t know where your edge weights are coming from   but much closer  If you want more control of how your output graph looks  e g  get arrowheads that look like arrows   I d check out NetworkX with Graphviz

[python] how to draw directed graphs using networkx in python?

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