Arched Relationship Infographic In Python

Question

This is a very specific inforgraphic challange altough the fundemental question is how do you build archs between words using matplotlib, cario or an other python libary.

Given a the following data structure.

me, you, 7 | me, apple, 9 | apple, you, 1 | bike, me, 5

Names would be displayed horizontally the names with the most relationships larger than the others and then there would be weighted archs between the names. A 10 weighted arch would be twice as thick as a 5 weighted arch.

Inspiration comes from: similar diverstiy. http://similardiversity.net/

Let the challange commence!

Answer 1

I don't really see where the difficulty or challenge is. All you need is a graphics library that can draw text and half circles, which is possible in pretty much everything. There is no need for Bezier curves. For example you could simply create an SVG file (then you don't even need any library and can nicely embed this in a webpage and use some JavaScript to make it interactive).

The actual plotting is trivial: the center of a circle is in the middle between the two words, the radius is half the distance between them. You can then adjust the stroke to reflect other quantities.

If you want somebody else to do the work for you then you should tag this as homework and maybe offer a bounty ;-)

Answer 2

matplotlib isn't the right library here, since it's not a general purpose graphics library. What you need here is either something like Cairo, or much simpler, you can do with the graphics capabilities of any GUI toolkit, such as PyQt. Another feasible approach is PyGame, which has good drawing capabilities as well.

If you want an example, see this Cairo samples page, the first sample - arc. You just write the text words and then use the arc code for an arc of any width and color between them.

Answer 3

There are several libraries, at least one of which relies on Matplotlib, that will do what you want. I recommend Networkx (www.networkx.lanl.gov) to build your graph structure, and which you can then use to call the relevant Matplotlib methods to plot. Networkx and Matplotlib work very well together.

import networkx as NX
import matplotlib.pyplot as PLT
Gh = NX.Graph()
Gh.add_edge("You", "Bike", weight=1.0)
Gh.add_edge("Bike", "Apple", weight=0.9)
Gh.add_edge("Me", "Bike", weight=1.1)
all_nodes = Gh.nodes()
# to scale node size with degree:
scaled_node_size = lambda(node) : NX.degree(Gh, node) * 700
position = NX.spring_layout(Gh)    # just choose a layout scheme
NX.draw_networkx_nodes(Gh, position, node_size=map(scaled_node_size, all_nodes))
NX.draw_network_edges(Gh, position, Gh.edges(), width=1.0, alpha=1.0, edge_color="red")
# now for the Matplotlib part:
PLT.axis("off")
PLT.show()

As you can see, you could scale the edges by applying a factor to vary the 'weight' parameter to any of the 'edge' methods, just the same way as i did it for node scaling.

I would also recommend pygraphviz (obviously using graphviz as its backend). It is very similar to Netwworkx (same lead developer).