matplotlib: Setting both major and minor ticks forces same x and y scale

Question

This question is related to the earlier question I asked "matplotlib: Change grid interval and specify tick labels" but now I want to change the scale for x and y axes. When I set the range for x and y axes and then specify the intervals for major and minor ticks, it forces the x and y axes to be the same.

This is my code.

import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.add_subplot(111)

for key, value in sorted(data.items()):
    x = value[0][2]
    y = value[0][3]
    count = value[0][4]

    ax.annotate(count, xy = (x, y), size = 3)

plt.suptitle('Number of counts', fontsize = 12)

ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_aspect('equal')

# I want max x axis to be 500
ax.set_xlim(0, 501)
# I want max y axis to be 300
ax.set_ylim(0, 301)

# I want major ticks to be every 20
major_ticks = np.arange(0, 501, 20)

# I want minor ticks to be every 5
minor_ticks = np.arange(0, 501, 5)
# If I do minor_ticks = np.arange(0, 301, 5), I will not get minor ticks for the entire plot

# Specify tick label size
ax.tick_params(axis = 'both', which = 'major', labelsize = 4)
ax.tick_params(axis = 'both', which = 'minor', labelsize = 0)
# Suppress minor tick labels

ax.set_xticks(major_ticks)
ax.set_xticks(minor_ticks, minor = True)
ax.set_yticks(major_ticks)
ax.set_yticks(minor_ticks, minor = True)

# Set both ticks to be outside
ax.tick_params(which = 'both', direction = 'out')

# Specify different settings for major and minor grids
ax.grid(which = 'minor', alpha = 0.3)
ax.grid(which = 'major', alpha = 0.7)

filename = 'C:\Users\Owl\Desktop\Plot.png'
plt.savefig(filename, dpi = 150)
plt.close()

and this is what I get.

How could I get different ranges for x and y axes and still have major and minor ticks like this? I might be missing something very simple but if somebody could point it out, I am very thankful for that!!

Answer 1

That's because you set the x and y ticks to the same thing. If you want different sizes, then you also need different ticks. You can't set both sets of ticks to the same major_ticks positions. Make one list of tick positions for the x axis and a separate list of tick positions for y axis and then set the ticks for each axis to the corresponding list.

Answer 2

I updated my code as below and now I get what I wanted! Thanks!

import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.add_subplot(111)

for key, value in sorted(data.items()):
    x = value[0][2]
    y = value[0][3]
    count = value[0][4]

    ax.annotate(count, xy = (x, y), size = 3)

plt.suptitle('Number of counts', fontsize = 12)

ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_aspect('equal')

# I want max x axis to be 500
ax.set_xlim(0, 501)
# I want max y axis to be 300
ax.set_ylim(0, 301)

# Set major ticks for x axis
major_xticks = np.arange(0, 501, 20)

# Set major ticks for y axis
major_yticks = np.arange(0, 301, 20)

# I want minor ticks for x axis
minor_xticks = np.arange(0, 501, 5)

# I want minor ticks for y axis
minor_yticks = np.arange(0, 301, 5)

# Specify tick label size
ax.tick_params(axis = 'both', which = 'major', labelsize = 6)
ax.tick_params(axis = 'both', which = 'minor', labelsize = 0)
# Suppress minor tick labels

ax.set_xticks(major_xticks)
ax.set_xticks(minor_yticks, minor = True)

ax.set_yticks(major_xticks)
ax.set_yticks(minor_yticks, minor = True)

# Set both ticks to be outside
ax.tick_params(which = 'both', direction = 'out')

# Specify different settings for major and minor grids
ax.grid(which = 'minor', alpha = 0.3)
ax.grid(which = 'major', alpha = 0.7)

filename = 'C:\Users\Owl\Desktop\Plot.png'
plt.savefig(filename, dpi = 150)
plt.close()