更改网格间隔并在Matplotlib中指定刻度标签

Question

我试图在网格图中绘制计数,但我无法弄清楚我是如何去做的.我想要:

1. 以5为间隔有网格

2. 每20个主要的刻度标签

3. 我希望刻度线在情节之外.

4. 在这些网格中"有计数"

我已经检查了这里和这里的潜在重复项,但是我还没弄清楚.

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.

我也有覆盖数据点的问题,我也遇到了麻烦......有人可以帮我解决这个问题吗？

Answer 1

您的代码中存在几个问题.

首先是大的:

1. 您正在循环的每次迭代中创建一个新图形和一个新轴→放置fig = plt.figure和ax = fig.add_subplot(1,1,1)循环外部.

2. 不要使用定位器.调用的函数ax.set_xticks(),并ax.grid()用正确的关键字.

3. 随着plt.axes()你再次创建一个新的轴.使用ax.set_aspect('equal').

小事:你不应该像plt.axis()使用客观语法那样混合类似MATLAB的语法.使用ax.set_xlim(a,b)和ax.set_ylim(a,b)

这应该是一个有用的最小例子:

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:

Answer 2

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=':')