pythonmatplotlibplotlogarithmyticks

semilogy plot does not proper color y-ticks


Issue is with semilogy, not with twinx. From next code

import numpy as np
import matplotlib.pyplot as plt
def plot_me(x):
    fig, ax1 = plt.subplots()
    ax1.semilogy(x, color="blue")
    for label in ax1.get_yticklabels():
        label.set_color("blue")

    ax2 = ax1.twinx()
    ax2.semilogy(1/x, 'red')
    for label in ax2.get_yticklabels():
        label.set_color("red")        

plot_me(np.arange(.1, 1.3, 1e-1)) goes through 1e-1 and 1e0 in left y-axis, through another two logs in right on. All ok:

enter image description here

on the other hand plot_me(np.arange(.1, .3, 1e-2)) does not pass at least two log10 (in neither left nor right y-axis), thus both axis got aside 1 log10 y-tick also non log10 y-ticks, which I cannot proper color: enter image description here

Furthermore, the y-ticks from a semilog are all log10, which contradict what we have seen in y-ticks labels of previous plots!

def print_y_ticks(x):
    fig, ax1 = plt.subplots()
    ax1.semilogy(x, color="blue")
    for label in ax1.get_yticklabels():
        label.set_color("blue")
    print(ax1.get_yticks())
    return ax1
    
ax = print_y_ticks(np.arange(.1, 1.3, 1e-1)) # [1.e-03 1.e-02 1.e-01 1.e+00 1.e+01 1.e+02]
ax = print_y_ticks(np.arange(.1, .3, 1e-2))  # [1.e-03 1.e-02 1.e-01 1.e+00 1.e+01]

My workaround is next:

import numpy as np
import matplotlib.pyplot as plt
def ticks2log(ax):
    yticks = ax.get_yticks()
    ax.set_yticks(yticks, [f'{k:.1e}' for k in yticks])
    return ax

def plot_me_new(x1, x2):
    x1 = np.log10(x1)
    x2 = np.log10(x2)

    fig, ax1 = plt.subplots()

    ax1.plot(x1, lw=2, color="blue")
    ax1 = ticks2log(ax1)
    for label in ax1.get_yticklabels():
        label.set_color("blue")

    ax2 = ax1.twinx()
    ax2.plot(x2, lw=2, color="red")
    ax2 = ticks2log(ax2)
    for label in ax2.get_yticklabels():
        label.set_color("red")

Result of x = np.arange(.1, .3, 1e-2); plot_me_new(x, 1/x) is proper colored, but much more tedious.

enter image description here

Thanks in advance for the help!

PD: issue is with semilogy, not with twinx.


Solution

  • ax.get_yticklabels(which='both')
    

    Solved by JohanC