Python 在 Matplotlib 中更改网格间隔并指定刻度标签
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Change grid interval and specify tick labels in Matplotlib
提问by owl
I am trying to plot counts in gridded plots, but I am not being able to figure out how I go about it. I want to:
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：
Have dotted grids at an interval of 5
Have major tick labels only every 20
I want the ticks to be outside the plot.
Have "counts" inside those grids
有间隔为 5 的虚线网格
只有每 20 个主要刻度标签
我希望刻度线在情节之外。
在这些网格内有“计数”
I have checked for potential duplicates such as hereand here, but I have not been able to figure it out.
This is my code.
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()
This is what I get.
这就是我得到的。
I also have a problem of overwriting the data points, which I am also having trouble with... Could anybody PLEASE help me with this problem?
我也有覆盖数据点的问题，我也遇到了问题......有人可以帮我解决这个问题吗？
采纳答案by MaxNoe
There are several problems in your code.
您的代码中有几个问题。
First the big ones:
首先是大的：
You are creating a new figure and a new axes in every iteration of your loop → put
fig = plt.figureandax = fig.add_subplot(1,1,1)outside of the loop.Don't use the Locators. Call the functions
ax.set_xticks()andax.grid()with the correct keywords.With
plt.axes()you are creating a new axes again. Useax.set_aspect('equal').
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.figure和ax = fig.add_subplot(1,1,1)环路以外。不要使用定位器。调用函数
ax.set_xticks()并ax.grid()使用正确的关键字。随着
plt.axes()您再次创建新轴。使用ax.set_aspect('equal').
The minor things:
You should not mix the MATLAB-like syntax like plt.axis()with the objective syntax.
Use ax.set_xlim(a,b)and ax.set_ylim(a,b)
小事：您不应该将类似 MATLAB 的语法plt.axis()与客观语法混合使用。使用ax.set_xlim(a,b)和ax.set_ylim(a,b)
This should be a working minimal example:
这应该是一个工作最小的例子：
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()
Output is this:
输出是这样的：
回答by getup8
A subtle alternative to MaxNoe's answerwhere you aren't explicitly setting the ticks but instead setting the cadence.
MaxNoe 答案的一种微妙替代方法，您没有明确设置刻度，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=':')
