Matplotlib 简明教程

Matplotlib - Tick Locators

在一般图形和绘图中，刻度在通过小线表示 x 和 y 轴的刻度方面发挥着至关重要的作用，从而清楚地指示相关的值。 Tick locators 另一方面，定义了这些刻度沿轴的位置，提供了刻度的可视表示。

In general graphs and plottings, ticks play a crucial role in representing the scale of x and y-axes through small lines, offering a clear indication of the associated values. Tick locators, on the other hand, define the positions of these ticks along the axis, offering a visual representation of the scale.

下图表示图形上的主刻度和次刻度 −

The below image represents the major and minor ticks on a graph −

tick locators input

Tick Locators in Matplotlib

matplotlib 通过其刻度定位器提供了一种控制刻度在轴上定位的机制。 matplotlib.ticker 模块包含用于配置刻度定位和格式化的类。这些类包括通用刻度定位器、格式化程序和特定于域的自定义定位器。虽然定位器不知道主刻度或次刻度，但它们被 Axis 类用于支持主刻度和次刻度定位和格式化。

Matplotlib provides a mechanism for controlling the positioning of ticks on axes through its tick locators. The matplotlib.ticker module contains classes for configuring tick locating and formatting. These classes include generic tick locators, Formatters, and domain-specific custom ones. While locators are unaware of major or minor ticks, they are used by the Axis class to support major and minor tick locating and formatting.

Different Tick Locators

matplotlib 在其 ticker 模块中提供了不同的刻度定位器，允许用户自定义轴上的刻度位置。一些刻度定位器包括 −

The matplotlib provides different tick locator within its ticker module, allowing users to customize the tick positions on axes. Some of the Tick Locators include −

  1. AutoLocator

  2. MaxNLocator

  3. LinearLocator

  4. LogLocator

  5. MultipleLocator

  6. FixedLocator

  7. IndexLocator

  8. NullLocator

  9. SymmetricalLogLocator

  10. AsinhLocator

  11. LogitLocator

  12. AutoMinorLocator

  13. Defining Custom Locators

Basic Setup

在深入研究具体刻度定位器之前，我们来建立一个通用的设置函数，用刻度绘制绘图。

Before diving into specific tick locators, let’s establish a common setup function to draw the plot with ticks.

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.ticker as ticker

def draw_ticks(ax, title):
   # it shows the bottom spine only
   ax.yaxis.set_major_locator(ticker.NullLocator())
   ax.spines[['left', 'right', 'top']].set_visible(False)

   ax.xaxis.set_ticks_position('bottom')
   ax.tick_params(which='major', width=1.00, length=5)
   ax.tick_params(which='minor', width=0.75, length=2.5)
   ax.set_xlim(0, 5)
   ax.set_ylim(0, 1)
   ax.text(0.0, 0.2, title, transform=ax.transAxes,
      fontsize=14, fontname='Monospace', color='tab:blue')

现在，让我们探讨每个刻度定位器的作用。

Now, let’s explore the working of each tick locator.

Auto Locator

AutoLocator 和 AutoMinorLocator 分别用于自动确定轴上的主刻度和次刻度的位置。

The AutoLocator and AutoMinorLocator are used for automatically determining the positions of major and minor ticks on an axis, respectively.

Example

此示例演示如何使用 AutoLocator 和 AutoMinorLocator 自动处理轴上的主刻度和次刻度的定位。

This example demonstrates how to use the AutoLocator and AutoMinorLocator to automatically handle the positioning of major and minor ticks on an axis.

# Auto Locator
fig, ax = plt.subplots(1,1,figsize=(7,1.5), facecolor='#eaffff')
plt.subplots_adjust(bottom=0.3, top=0.6, wspace=0.2, hspace=0.4)
draw_ticks(ax, title="AutoLocator() and AutoMinorLocator()")
ax.xaxis.set_major_locator(ticker.AutoLocator())
ax.xaxis.set_minor_locator(ticker.AutoMinorLocator())
ax.set_title('Auto Locator and Auto Minor Locator')
plt.show()
tick locators ex1

Null Locator

NullLocator 在轴上不放置刻度。

The NullLocator places no ticks on the axis.

Example

我们来看以下 NullLocator 工作示例。

Let’s see the following example for working of the NullLocator.

# Null Locator
fig, ax = plt.subplots(1,1,figsize=(7,1.5), facecolor='#eaffff')
plt.subplots_adjust(bottom=0.3, top=0.6, wspace=0.2, hspace=0.4)
draw_ticks(ax, title="NullLocator()")
ax.xaxis.set_major_locator(ticker.NullLocator())
ax.xaxis.set_minor_locator(ticker.NullLocator())
ax.set_title('Null Locator (No ticks)')
plt.show()
tick locators ex2

Multiple Locator

MultipleLocator() 类允许以指定基数的倍数放置刻度，同时支持整型和浮点值。

The MultipleLocator() class allows ticks to be positioned at multiples of a specified base, supporting both integer and float values.

Example

以下示例演示了 MultipleLocator() 类的使用方法。

The following example demonstrates how to use the MultipleLocator() class.

# Multiple Locator
fig, ax = plt.subplots(1,1,figsize=(7,1.5), facecolor='#eaffff')
plt.subplots_adjust(bottom=0.3, top=0.6, wspace=0.2, hspace=0.4)
draw_ticks(ax, title="MultipleLocator(0.5)")
ax.xaxis.set_major_locator(ticker.MultipleLocator(0.5))
ax.xaxis.set_minor_locator(ticker.MultipleLocator(0.1))
ax.set_title('Multiple Locator')
plt.show()
tick locators ex3

Fixed Locator

FixedLocator() 将刻度放置在指定固定位置。

The FixedLocator() places ticks at specified fixed locations.

Example

以下是如何使用 FixedLocator() 类的示例。

Here is an example of using the FixedLocator() class.

# Fixed Locator
fig, ax = plt.subplots(1,1,figsize=(7,1.5), facecolor='#eaffff')
plt.subplots_adjust(bottom=0.3, top=0.6, wspace=0.2, hspace=0.4)
draw_ticks(ax, title="FixedLocator([0, 1, 3, 5])")
ax.xaxis.set_major_locator(ticker.FixedLocator([0, 1, 3, 5]))
ax.xaxis.set_minor_locator(ticker.FixedLocator(np.linspace(0.2, 0.8, 4)))
ax.set_title('Fixed Locator')
plt.show()
tick locators ex4

Linear Locator

LinearLocator 在最大值和最小值之间均匀分布刻度。

The LinearLocator spaces ticks evenly between specified minimum and maximum values.

Example

以下示例应用线性定位器到轴线的主刻度和次刻度。

Here is an example that applies the Linear Locator to the major and minor ticks of an axes.

# Linear Locator
fig, ax = plt.subplots(1,1,figsize=(7,1.5), facecolor='#eaffff')
plt.subplots_adjust(bottom=0.3, top=0.6, wspace=0.2, hspace=0.4)
draw_ticks(ax, title="LinearLocator(numticks=3)")
ax.xaxis.set_major_locator(ticker.LinearLocator(3))
ax.xaxis.set_minor_locator(ticker.LinearLocator(10))
ax.set_title('Linear Locator')
plt.show()
tick locators ex5

Index Locator

该定位器适用于 x = range(len(y)) 的索引图。

This locator is suitable for index plots, where x = range(len(y)).

Example

以下示例使用了索引定位器 ( ticker.IndexLocator() 类)。

Here is an example that uses the index loctator (ticker.IndexLocator() class).

# Index Locator
fig, ax = plt.subplots(1,1,figsize=(7,1.5), facecolor='#eaffff')
plt.subplots_adjust(bottom=0.3, top=0.6, wspace=0.2, hspace=0.4)
draw_ticks(ax, title="IndexLocator(base=0.5, offset=0.25)")
ax.plot([0]*5, color='white')
ax.xaxis.set_major_locator(ticker.IndexLocator(base=0.5, offset=0.25))
ax.set_title('Index Locator')
plt.show()
tick locators ex6

MaxN Locator

Example

以下示例演示如何将 MaxNLocator() 类用于主刻度和次刻度。

Here is an example of using the MaxNLocator() class for both major and minor ticks.

# MaxN Locator
fig, ax = plt.subplots(1,1,figsize=(7,1.5), facecolor='#eaffff')
plt.subplots_adjust(bottom=0.3, top=0.6, wspace=0.2, hspace=0.4)
draw_ticks(ax, title="MaxNLocator(n=4)")
ax.xaxis.set_major_locator(ticker.MaxNLocator(4))
ax.xaxis.set_minor_locator(ticker.MaxNLocator(40))
ax.set_title('MaxN Locator')
plt.show()
tick locators ex7

Log Locator

LogLocator 用于以从最小值到最大值的对数方式分布刻度。

The LogLocator is used for spacing ticks logarithmically from min to max.

Example

我们来看一个使用对数定位器的示例。它显示的对数刻度的次刻度标签。

Let’s see an example of using the Log Locator. It shows the minor tick labels on a log-scale.

# Log Locator
fig, ax = plt.subplots(1,1,figsize=(7,1.5), facecolor='#eaffff')
plt.subplots_adjust(bottom=0.3, top=0.6, wspace=0.2, hspace=0.4)
draw_ticks(ax, title="LogLocator(base=10, numticks=15)")
ax.set_xlim(10**3, 10**10)
ax.set_xscale('log')
ax.xaxis.set_major_locator(ticker.LogLocator(base=10, numticks=15))
ax.set_title('Log Locator')
plt.show()
tick locators ex8