Managing subplots

Recommended way of creating subplots

In academic works, people usually compose a single figure with multiple subplots, sometimes to facilitate comparisons, but mostly to make the most of the valuable real estates of a graph.

There are more than one ways of creating subplots in matplotlib. For usage with gplot, the recommended way of creating subplots is:

figure, axes = plt.subplots(nrows=2, ncols=2, constrained_layout=True)

The returned axes is a 2D array, holding the axes for a 2x2 grid layout. To iterate through the axes, one can use:

for ii, axii in enumerate(axes.flat):
    rowii, colii = np.unravel_index(ii, (nrows, ncols))
    ...

Note

the constrained_layout=True argument is recommended. This will adjust the spacings of the subplots to avoid overlaps between subplots, and wasted spaces as well. Do not use figure.tight_layout() afterwards, as it tends to mess up the placement of a shared, global colorbar.

Note

the placement of a globally shared colorbar is currently not as robust as a local colorbar. One may find the global colorbar tick labels overlaping with those in the bottom row x-axis, if the constrained_layout is not set to True.

Automatically label the subplots with alphabetic indices

The title input argument to the base_utils.Plot2D constructor or the base_utils.plot2() function is used to label the subplots. It is defaulted to None. The clean argument also has some effects. They function a bit differently in different scenarios:

• title = None:

  • If figure has only 1 subplot: no title is drawn.

  • If figure has more than 1 subplots, an alphabetic index is used as the subplot title, e.g. (a) for the 1st subplot, (b) for the 2nd, and so on. The order is row-major. After using up all the 26 letters, it will cycle through them again but with 2 letters at a time, e.g. (aa) for the 27th subplots. This rarely happens in practice.

• title = some_text:

  • If figure has only 1 subplot: use some_text as the title.

  • If figure has more than 1 subplots, an alphabetic index is prepended to form the subplot title: (a) some_text. An example of this can be seen here.

• title = (x) some_text:

  Where x is an arbitrary string. Use (x) some_text as the title. This can be used to override the automatic row-major ordering of the subplot indices. For instance, you want to label it as (k) when the subplot is at a position of (h).

• title = 'none' or clean = True: no title is drawn in any circumstances.