Question

With the help of sankey-toolbox in Matplotlib, we can plot sankey-diagrams automaticly: The position of a sankey-object is automaticly calculated based on the position of its prior-object and cannot be given manually; and when a sankey-diagram is initialized, the position of the first sankey-object will be assigned with the input of an axis. (the (0,0)-point will be the center-point of this object)

And Here is the situation: i want to draw two sankey diagrams with a given y-offset, and several ports of the two diagrams should be connected. Therefore are two coordinate systems with y-offset in the same subplot required. I have tried the ‘add_axes‘ method, but with this method a new subplot is created and there will be a graphic scaling problem.

Now this is the question: Is it possible to create a new coordinate system with a given y-offset, without creating subplot?

Answer 1

Not really a complete answer, but it might help you to find the solution:
sankey.add() supports a transform keyword argument. Depending on your figure, create a new transform instance, and use it for the shifted part of your figure:

offset = transforms.ScaledTranslation(0.0, 0.5, fig.dpi_scale_trans)
new_transform = ax.transData + offset
sankey.add(flows=[-0.25, 0.15, 0.1], fc='#37c959', label='two',
           orientations=[-1, -1, -1], prior=0, connect=(0, 0),
           transform = new_transform)

In order to create the new transform, the helper function matplotlib.transforms.offset_copy() may also be useful:

new_transform = offset_copy(ax.transData, fig=fig,
                            x = 0.05, y=0.10, units='inches')