Data analysis - Matplotlib sample code

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt


x = np.linspace(-2, 2, 100)
y1 = np.cos(np.pi * x)
y2 = np.sin(np.pi * x)
plt.plot(x, y1, "go", label=r"$y1=\cos(\pi \times x)$", alpha=0.8, linewidth=0.7)
plt.plot(x, y2, "r-", label=r"$y2=\sin(\pi \times x)$", alpha=0.8, linewidth=0.7)
df = pd.DataFrame(np.random.randint(0, 100, size=(100, 1)), columns=list('A'))

plt.annotate("important Point", (0, 1), xytext=(-1.5, 1.1), arrowprops=dict(arrowstyle='->'))

plt.xlabel("x-axis")
plt.ylabel("y-axis")

#  Set the coordinate range [xmin, xmax, ymin, ymax]
plt.axis([-2.1, 2.1, -1.2, 1.2])

#  Show labels 
plt.legend()
#  Show grid 
plt.grid(alpha=0.4)
plt.title("Two Plots", color=(0.1, 0.3, 0.5))
plt.show()

The operation input is shown in the figure below ： 

Generally used is pyplot, And it is imported as plt.

● plt.plot(x,y,＇go')

This is quite clear ,x、y Are independent variable and dependent variable data . hinder ＇go＇ Is the control of style ： among g Indicates that green is selected ,o It shows the way of selecting points . For more parameter settings, use the help command help（plt.plot） Further study .

● plt.title(r＂$y=\cos(\pi\times x)$＂) Add a title to the diagram .

It is worth noting that , It's used here LaTeX The format of , because matplotlib Is compatible LaTeX Of . This provides great convenience for writing formulas . Readers may encounter situations where Chinese cannot be displayed , This point will be specially explained next .

● plt.show()

adopt show To show the images , stay pandas and seaborn This code is also used in Display the image .

● alpha

alpha Parameters represent transparency , from 0 To 1 Indicates that the color gradually deepens .

● linewidth

Represents the thickness of lines or points .

● axis

according to （xmin、xmax、ymin、ymax） To limit the range of coordinate axes .

● legend

stay plot It uses lable, The legend of the current figure is recorded , You can call legend Make it show . By default , The illustration will be displayed in the most appropriate blank space , Of course, its position can also be adjusted manually .

● grid Show background gridlines , It can also be done through alpha Parameter to set its transparency .

● color=(0.1,0.3,0.5)

In some cases ,matplotlib Its own color can't achieve the effect , At this time, it can be normalized to [0,1] Of RGB Tuples to specify colors . You can also use HTML The hexadecimal string of , Such as ＂＃eeefffff＂ To specify the color .

2. Chinese display problem

In the first use matplotlib Generally, you will encounter the problem that you cannot display Chinese , Whether it's Windows still Ubuntu And so on. Linux System .

about Windows, The solution is relatively simple , Just add the following three lines of code at the beginning , It's OK in general .

import matplotlib as mpl
mpl.rcParams["font.sans-serif"] = ["Microsoft YaHei"]
mpl.rcParams['axes.unicode_minus'] = False

  about Ubuntu System , You need to manually specify the font to realize the display of Chinese . The setup code is as follows .