更改网格间隔并在Matplotlib中指定刻度标签


82

我正在尝试在网格图中绘制计数,但是我无法弄清楚如何进行计算。我想要:

  1. 虚线网格间隔为5

  2. 每20个仅带有主要刻度线标签

  3. 我希望刻度线不在情节之外。

  4. 在这些网格内有“计数”

我已经检查了潜在的重复项,例如此处此处,但我无法弄清楚。

这是我的代码。

import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator, FormatStrFormatter

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

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

    ax.annotate(count, xy = (x, y), size = 5)
    # Overwrites and I only get the last data point

    plt.close()
    # Without this, I get "fail to allocate bitmap" error

plt.suptitle('Number of counts', fontsize = 12)
ax.set_xlabel('x')
ax.set_ylabel('y')
plt.axes().set_aspect('equal')

plt.axis([0, 1000, 0, 1000])
# This gives an interval of 200

majorLocator   = MultipleLocator(20)
majorFormatter = FormatStrFormatter('%d')
minorLocator   = MultipleLocator(5)
# I want minor grid to be 5 and major grid to be 20
plt.grid()

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

这就是我得到的。

这就是我得到的。

我也有覆盖数据点的问题。有人可以帮我解决这个问题吗?

Answers:


186

您的代码中有几个问题。

首先是大的:

  1. 您正在创建一个新的人物,在你的循环→把每一次迭代一个新的轴fig = plt.figureax = fig.add_subplot(1,1,1)环路以外。

  2. 不要使用定位器。调用函数ax.set_xticks()ax.grid()使用正确的关键字。

  3. 随着plt.axes()您再次创建新的轴。使用ax.set_aspect('equal')

较小的事情:您不应将类似于MATLAB的语法plt.axis()与目标语法混在一起。使用ax.set_xlim(a,b)ax.set_ylim(a,b)

这应该是一个最小的工作示例:

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)

# Major ticks every 20, minor ticks every 5
major_ticks = np.arange(0, 101, 20)
minor_ticks = np.arange(0, 101, 5)

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

# And a corresponding grid
ax.grid(which='both')

# Or if you want different settings for the grids:
ax.grid(which='minor', alpha=0.2)
ax.grid(which='major', alpha=0.5)

plt.show()

输出是这样的:

结果


2
非常感谢您的回答!您解决了我的问题!要将刻度线设置在外面,我只需要添加ax.tick_params(哪个=“两个”,方向=“向外”)。
猫头鹰2014年

29

MaxNoe答案的一种微妙替代方案,您无需显式设置刻度,而是设置节奏。

import matplotlib.pyplot as plt
from matplotlib.ticker import (AutoMinorLocator, MultipleLocator)

fig, ax = plt.subplots(figsize=(10, 8))

# Set axis ranges; by default this will put major ticks every 25.
ax.set_xlim(0, 200)
ax.set_ylim(0, 200)

# Change major ticks to show every 20.
ax.xaxis.set_major_locator(MultipleLocator(20))
ax.yaxis.set_major_locator(MultipleLocator(20))

# Change minor ticks to show every 5. (20/4 = 5)
ax.xaxis.set_minor_locator(AutoMinorLocator(4))
ax.yaxis.set_minor_locator(AutoMinorLocator(4))

# Turn grid on for both major and minor ticks and style minor slightly
# differently.
ax.grid(which='major', color='#CCCCCC', linestyle='--')
ax.grid(which='minor', color='#CCCCCC', linestyle=':')

Matplotlib自定义网格

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