Colour bar or legend...

[nickschurch]

Hi all,

I'm really new to networkX but I'be been playing with it for a bit and
getting some good results. I have a network that I plot with colours
based on the pvalue associated with an expression value - is there any
way to add a colourbar, or a legend to the plot to show the range pf
pvalues displayed?

Nick

[Dan Schult]

That would be a function in matplotlib (assuming you are using the
matplotlib drawing features of NetworkX).

Check out:
matplotlib.pyplot.colorbar()

http://matplotlib.sourceforge.net/api/
pyplot_api.html#matplotlib.pyplot.colorbar

That page has a lot of other nice drawing capabilities for matplotlib
that you will enjoy exploring. :) Since NetworkX uses matplotlib
any of them should work with your project.
Dan

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[nickschurch]

Thanks for the response! Colorbar seems to work, in that it does
indeed draw a colour bar, but it draws it for the edge colour values,
not for the node colour values. I can't see anything in the colorbar
api or documentation that allows you do choose which values of a graph
it applies to or allows you to foce a range for it. Any ideas?

[nickschurch]

Interestingly, if you don't specify edge colours then it will plot the
colorbar for the node values... I wonder if its because networkX plots
the edges after the nodes....

[Aric Hagberg]

On Mon, Feb 22, 2010 at 5:23 AM, nickschurch <nicks...@googlemail.com> wrote:
> Interestingly, if you don't specify edge colours then it will plot the
> colorbar for the node values... I wonder if its because networkX plots
> the edges after the nodes....

That is the reason. With a little more work you can control which
colorbar (you can even have 2). e.g.

import matplotlib.pyplot as plt
import networkx as nx

G=nx.star_graph(20)
pos=nx.spring_layout(G)
node_colors=range(21)
edge_colors=range(20)
nodes=nx.draw_networkx_nodes(G,pos,node_color=node_colors,cmap=plt.cm.Reds)
edges=nx.draw_networkx_edges(G,pos,edge_color=edge_colors,width=4,edge_cmap=plt.cm.Blues)
plt.sci(nodes)
plt.colorbar()
plt.sci(edges)
plt.colorbar()
plt.show() # display

Aric

[nickschurch]

Thanks Aric - I wasn't aware I could plot each part separately putting
a colourbar with each! Nice!

On 22 Feb, 14:32, Aric Hagberg <ahagb...@gmail.com> wrote:

[Uli]

Hi,

I try to get a legend with '^' marker, colors and textlabels to my graph.

I tried many ways, in the end getting a proper legend with markers and labels but without the proper colors.

It always seems to show the max. colorindex of the colormap. 

Using this example I succeeded in putting a colorbar to my graph with the proper colors but labeled by colorindex and not by label.

so how to get a legend to it. 

The result is a legend with proper labels, lines instead of '^' and wrong colors.

colors is a [1,2,2,5,3,...]

edgecolors is a [1,1,1,1,1...]

cmapC = matplotlib.cm.get_cmap('Spectral')

nc = nx.draw_networkx_nodes(GM,graph_pos,node_size=200, node_text_size=6, node_shape='^',

   alpha=1.0, node_color=colors, cmap=cmapC )   #      , label = "Orte"

ne = nx.draw_networkx_edges(GM,graph_pos,width=0.3,

   alpha=1.0,edge_color=edgecolors, edge_cmap=plt.cm.Blues, arrows=False)

nl = nx.draw_networkx_labels(GM, graph_pos, labels=Place_labels, font_size=6)

plt.axis('on')

plt.sci(nc)

plt.colorbar()

plt.legend(scatterpoints=1)

plt.sci(ne)

plt.colorbar()

plt.legend()

plt.show()