Hello,
I'm using graph-tool to create demonstrations of how a few graph coloring algorithms work. To do so, I'm creating snapshot images at each step of the coloring process.
While pinning the vertices' positions is trivial, I couldn't find a nice solution to "pin the colors": every time a new color is used, the normalization process picks new colors for all vertices, giving the false impression that the algorithm has changed them.
The code sample below probably explains the problem better: it creates files ex-vcolor-{0,1,2}.png showing that the vertex color changes:
g = Graph(directed=False) v_color = g.new_vertex_property("int") g.add_vertex(3) g.add_edge_list([(0,1),(1,2),(2,0)]) pos = sfdp_layout(g) for v in g.vertices(): v_color[v] = int(v) graph_draw(g, vertex_fill_color=v_color, pos=pos, output="ex-vcolor-" + str(int(v)) + ".png")
What I would like to have is: use the normalization process only once for n colors (to pick "spaced" colors) and then stick to them even when just a few are used in the graph being draw. Is this possible? Any ideas?
Thanks, Leonardo
PS. And thanks a lot for graph-tool! It is a real time saver :-)
On 17.11.2014 11:56, Leonardo Chiquitto wrote:
While pinning the vertices' positions is trivial, I couldn't find a nice solution to "pin the colors": every time a new color is used, the normalization process picks new colors for all vertices, giving the false impression that the algorithm has changed them.
The colors do not have to be simple scalar values, they can also be strings such as "green" or "#00FF00" or RGBA vectors such as [0., 1., 0., 1.]. That means you can set the color by hand, and avoid the normalization. For example:
color = g.new_vertex_property("vector<double>") color[g.vertex(0)] = [.1, .9, .1, 1.] color[g.vertex(1)] = [.9, .0, .1, 1.] ... graph_draw(g, vertex_fill_color=color)
Another option is to construct your own colormap, and pass it as the vcmap parameter. You can learn more about color maps here:
http://matplotlib.org/users/colormaps.html
Best, Tiago
On Mon, Nov 17, 2014 at 11:49 AM, Tiago de Paula Peixoto tiago@skewed.de wrote:
On 17.11.2014 11:56, Leonardo Chiquitto wrote:
While pinning the vertices' positions is trivial, I couldn't find a nice solution to "pin the colors": every time a new color is used, the normalization process picks new colors for all vertices, giving the false impression that the algorithm has changed them.
The colors do not have to be simple scalar values, they can also be strings such as "green" or "#00FF00" or RGBA vectors such as [0., 1., 0., 1.]. That means you can set the color by hand, and avoid the normalization. For example:
color = g.new_vertex_property("vector<double>") color[g.vertex(0)] = [.1, .9, .1, 1.] color[g.vertex(1)] = [.9, .0, .1, 1.] ... graph_draw(g, vertex_fill_color=color)
Thanks! This is exactly what I was looking for.
Leonardo
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Leonardo Chiquitto -
Tiago de Paula Peixoto