Matplotlib：在一组 arrays 上循环散布 plot，具有一致的散点大小和颜色条

Question

I am trying to generate a scatter plot using dataframe series x & y and the size of the scatter data point using dataframe series z.

I should mention that I iterate through a set of each x,y, and z arrays and add the color plot outside the loop.

I see that the scatter sizes and color bar are generated at each iteration therefore scatter sizes are not consistent with all data points in the plot and also with the colorbar at the end. How do I solve this?

fig, ax = plt.subplots()
for x, y, z in arrays_of_xyz:
     splot = ax.scatter(x.to_numpy(), y.to_numpy(),  marker= 'o', s = z.to_numpy(), cmap ='viridis_r', c = z.to_numpy())

fig.tight_layout()
plt.colorbar(splot)
plt.show()

Gautham

Answer 1

Can't see in which way the sizes in the plot are inconsistent. The colorbar can be inconsistent if you do not enforce consistent vmin and vmax when calling scatter .

Can you please try with the following code and tell more about inconsistencies you got:

import numpy as np
import matplotlib.pyplot as plt

num_sets = 3
colors = ("red", "green", "blue")
num_pts_per_set = 20

xs = np.random.randn(num_sets, num_pts_per_set)
ys = np.random.randn(num_sets, num_pts_per_set)
zs = (
    np.random.rand(num_sets, num_pts_per_set)
    * np.arange(1, num_sets + 1).reshape(-1, 1)
    * 30
)
zmin = zs.min()
zmax = zs.max()

fig, (ax1, ax2) = plt.subplots(ncols=2)

ax1.set_title("Sizes according to z\nColors according to set #")
for i, (x, y, z, clr) in enumerate(zip(xs, ys, zs, colors)):
    ax1.scatter(x, y, marker="o", s=z, c=clr, label=f"Set #{i}")
ax1.legend()

ax2.set_title("Facecolors according to z\nSizes according to set #")
for i, (x, y, z, clr) in enumerate(zip(xs, ys, zs, colors)):
    splot = ax2.scatter(x, y, marker="o", c=z, edgecolors=clr, s=(i+1)*30, vmin=zmin, vmax=zmax, label=f"Set #{i}")
ax2.legend()
fig.colorbar(splot)

plt.show()