Plot a map of classifications

This is an example showing how to produce a map showing the spatial distribution of spectral classifications in a 2D region of the Sun.

First we shall create a random 3D grid of classifications that can be plotted. Usually you would use a method such as mcalf.models.ModelBase.classify_spectra() to classify an array of spectra.

from mcalf.tests.helpers import class_map as c

t = 3  # Three images
x = 50  # 50 coordinates along x-axis
y = 20  # 20 coordinates along y-axis
n = 5  # Possible classifications [0, 1, 2, 3, 4]

class_map = c(t, x, y, n)  # 3D array of classifications (t, y, x)

Next, we shall import mcalf.visualisation.plot_class_map().

from mcalf.visualisation import plot_class_map

We can now simply plot the 3D array. By default, the first dimension of a 3D array will be averaged to produce a time average, selecting the most common classification at each (x, y) coordinate.

plot_class_map(class_map)

Out:

<matplotlib.image.AxesImage object at 0x7fcfe03d53a0>

A spatial resolution with units can be specified for each axis.

import astropy.units as u

plot_class_map(class_map, resolution=(0.75 * u.km, 1.75 * u.Mm),
               offset=(-25, -10),
               dimension=('x distance', 'y distance'))

Out:

<matplotlib.image.AxesImage object at 0x7fcfe2c234f0>

A narrower range of classifications to be plotted can be requested with the vmin and vmax parameters. Classifications outside of the range will appear as grey, the same as pixels with a negative, unassigned classification.

plot_class_map(class_map, vmin=1, vmax=3)

Out:

<matplotlib.image.AxesImage object at 0x7fcfe0302970>

An alternative set of colours can be requested. Passing a name of a matplotlib colormap to the style parameter will produce a corresponding list of colours for each of the classifications. For advanced use, explore the cmap parameter.

plot_class_map(class_map, style='viridis')

Out:

<matplotlib.image.AxesImage object at 0x7fcfe05f93a0>

The plot_class_map function integrates well with matplotlib, allowing extensive flexibility. This example also shows how you can plot a 2D class_map and skip the averaging.

import matplotlib.pyplot as plt

fig, ax = plt.subplots(2, constrained_layout=True)

plot_class_map(class_map[0], style='viridis', ax=ax[0],
               show_colorbar=False)
plot_class_map(class_map[1], style='viridis', ax=ax[1],
               colorbar_settings={'ax': ax, 'label': 'classification'})

ax[0].set_title('time $t=0$')
ax[1].set_title('time $t=1$')

plt.show()