0

I'm using the wonderful OSMnx library created by Geoff Boeing. I am plotting a street network based on one of his tutorials. Everything works perfectly. However, I would like to plot more than 40 graphs, using different centralities. Therefore, I would like to add a title with each district and centrality name to each plot. Currently, it looks like this.

Plotted OSMnx Street Network

This is what my code looks like.

def display_most_important_node(G_centralities_sorted_dict, G_dictionary, district, centrality_measure='betweenness_centrality'):
    node_color = ['red' if node == G_centralities_sorted_dict[district][centrality_measure][0][0] else '#336699' for node in ox.project_graph(G_dictionary[district]).nodes()]
    node_size = [40 if node == G_centralities_sorted_dict[district][centrality_measure][0][0] else 20 for node in ox.project_graph(G_dictionary[district]).nodes()]

    fig, ax = ox.plot_graph(ox.project_graph(G_dictionary[district]), annotate=False, edge_linewidth=1.5, node_size=node_size, fig_height=10, node_color=node_color, node_zorder=2)

Thank you guys.

Thomas Kühn
  • 9,412
  • 3
  • 47
  • 63
ck12
  • 53
  • 4
  • 1
    Welcome to Stackoverflow. Unfortunately it is quite hard to help you with the code you show. Please post your problem as [Minimal, Complete, and Verifiable example](https://stackoverflow.com/help/mcve) and explain clearly what doesn't work. This way you will receive help much quicker. – Thomas Kühn Feb 15 '18 at 07:16
  • Hey @ThomasKühn. Thanks a bunch for your input. I've updated my initial post and hope it's more clear now. – ck12 Feb 15 '18 at 18:36
  • I don't know that library, but it looks like what `ox.plot_graph` returns is a `pyplot.Figure` and a `pyplot.Axes`. If that is true, you should be able to use the normal matplotlib functions on these methods. Try if `ax.set_title('the title')` or `fig.suptitle('the other title')` does what you want. – Thomas Kühn Feb 15 '18 at 18:45
  • Thank you @ThomasKühn. That was my initial thought. Unfortunately, it didn't work. I also tried `fig.text(.73, .834, 'title', fontsize=16)` but again no success. – ck12 Feb 15 '18 at 18:59
  • I had a look at the source code and the `fig, ax` tuple is indeed generated with `plt.subplots()`, but the function calls `plt.show()` itself by default. Try adding the keywords `show=False` and `close = False` to your `ox.plot_graph` call. Then, do `ax.set_title('test')` and then do `plt.show()`. – Thomas Kühn Feb 15 '18 at 19:41
  • It worked! You are amazing @ThomasKühn. Thank you so much! – ck12 Feb 15 '18 at 21:32
  • No problem. I formulated it as an answer. – Thomas Kühn Feb 16 '18 at 05:00

1 Answers1

4

By default, the functions of the OSMnx package call plt.show() already before they return the fig and ax handles, which means you can no longer manipulate the Figure and Axes instances (my guess is that this is done to prevent distortion of the Figure after creation). This is done using a special function called save_and_show(), which is called internally. You can prevent the showing of the figure by passing the keywords show=False and close=False to the according plotting function (close=False is needed because figures that are not automatically shown are by default closed within save_and_show()). With these keywords used, fig and ax can be manipulated after the function call, but now plt.show() has to be called explicitly. Here still a complete example following the OP:

def display_most_important_node(G_centralities_sorted_dict, G_dictionary, district, centrality_measure='betweenness_centrality'):
    node_color = ['red' if node == G_centralities_sorted_dict[district][centrality_measure][0][0] else '#336699' for node in ox.project_graph(G_dictionary[district]).nodes()]
    node_size = [40 if node == G_centralities_sorted_dict[district][centrality_measure][0][0] else 20 for node in ox.project_graph(G_dictionary[district]).nodes()]

    fig, ax = ox.plot_graph(ox.project_graph(G_dictionary[district]), annotate=False, edge_linewidth=1.5, node_size=node_size, fig_height=10, node_color=node_color, node_zorder=2, show=False, close=False)

    ax.set_title('subplot title')
    fig.suptitle('figure title')
    plt.show()

Note that not all OSMnx functions accept the show and close keywords. For instance, plot_shape does not. Hope this helps.

Thomas Kühn
  • 9,412
  • 3
  • 47
  • 63