I am drawing different circles with Matplotlib. Each circle has a label, and each label has a colour. What can I do to have a colourmap legend for these different labels?
I have tried a lot of solutions online, including the most naive one by just adding plt.colorbar(), which I will get the error
RuntimeError('No mappable was found to use for colorbar')
Here is my complete code. It's a little bit long. Please note that the key part just starts from if labels is None:. I just include everything for completeness.
def plot_gaussian_circles(loc_list, scale_list, save_path=None, sigma_coe=3, num_to_plot=300, labels=None):
mu_x_max = -float('inf')
mu_y_max = -float('inf')
mu_x_min = float('inf')
mu_y_min = float('inf')
color_idx = 0
rvs = []
lim_loc_list = loc_list[:num_to_plot]
lim_scale_list = scale_list[:num_to_plot]
for a_mu_, a_sigma_ in zip(lim_loc_list, lim_scale_list):
a_mu = a_mu_.squeeze()
a_sigma_ = a_sigma_.squeeze()
if not type(a_sigma_) is np.ndarray:
a_sigma_ = a_sigma_.numpy()
radius = sigma_coe * np.max(a_sigma_)
a_mu_x = a_mu[0]
a_mu_y = a_mu[1]
if (a_mu_x + radius) >= mu_x_max:
mu_x_max = a_mu_x + radius
if (a_mu_x - radius) <= mu_x_min:
mu_x_min = a_mu_x - radius
if (a_mu_y + radius) >= mu_y_max:
mu_y_max = a_mu_y + radius
if (a_mu_y - radius) <= mu_y_min:
mu_y_min = a_mu_y - radius
if labels is None:
rv = plt.Circle(a_mu, radius, fill=False, clip_on=False)
else:
colors = cm.rainbow(np.linspace(0, 1, len(set(labels))))
rv = plt.Circle(a_mu, radius, color=colors[labels[color_idx]], fill=False, clip_on=False)
rvs.append(rv)
color_idx = (color_idx + 1)
fig, ax = plt.subplots()
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')
axes = plt.gca()
axes.set_xlim([mu_x_min - 1, mu_x_max + 1])
axes.set_ylim([mu_y_min - 1, mu_y_max + 1])
for rv in rvs:
ax.add_artist(rv)
if not(labels is None):
# plt.legend(colors, list(range(len(set(labels)))))
plt.colorbar()
if save_path is None:
plt.plot()
plt.show()
# plt.savefig('plotcircles_test.png')
else:
plt.savefig(save_path, dpi=200)
The image here is currently what I am getting, while I wish to have a legend of the colormap. 
