How to make a scatter plot of different sizes, colour, and positions?

Question

How to make a scatter plot with random values of delta_x and delta_y positions; where each point has certain frequency value(color intensity changes depending upon intensity), i.e., a certain symbols.

Example plot: (from Alberdi, et al, 2013)

Answer 1

If I'm understanding you correctly, you're asking how to have scatter share a color scale but have different symbols for different groups, correct?

There are a few different ways to handle this.

The key is to call scatter multiple times (one for each different group), but pass in the same vmin, vmax, and cmap arguments.

As an complete (and arguably over-complex) example of reproducing the plot above:

import numpy as np
import matplotlib.pyplot as plt

# Generate data
freq_groups = [1.7, 2.3, 5.0, 8.4]
num = 50
x = np.random.normal(0, 0.5, num)
y = np.random.normal(0.2, 0.5, num)
year = 9 * np.random.random(num) + 1993.5
frequencies = np.random.choice(freq_groups, num)

symbols = ['o', '^', 's', 'd']

# Plot data
fig, ax = plt.subplots(figsize=(8, 9))
for freq, marker in zip(freq_groups, symbols):
    mask = np.isclose(freq, frequencies)
    scat = ax.scatter(x[mask], y[mask], c=year[mask], s=100, marker=marker,
                      cmap='jet_r', vmin=year.min(), vmax=year.max(),
                      label='{:0.1f} GHz'.format(freq), color='black')

ax.legend(loc='upper left', scatterpoints=1)
ax.set(xlabel='Relative RA (mas)', ylabel='Relative Dec (mas)')
ax.invert_xaxis()
cbar = fig.colorbar(scat, orientation='horizontal')
cbar.set_label('Epoch (year)')
cbar.formatter.useOffset = False
cbar.update_ticks()
fig.tight_layout()

plt.show()