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Matplotlib drawing core principles explain (more detailed)

2022-08-03 00:38:00 【51CTO】

1、核心原理讲解

matplotlibThe core principle of drawing on(超详细)_matplotlib绘图原理

使用matplotlibThe principle of drawing,主要就是理解figure(画布)、axes(坐标系)、axis(坐标轴)三者之间的关系.

matplotlibThe core principle of drawing on(超详细)_matplotlib_02

Zhang SAN's sketchpad

matplotlibThe core principle of drawing on(超详细)_图形绘制_03

matplotlib绘图

matplotlibThe core principle of drawing on(超详细)_matplotlib_04

2、matplotlib库的安装与导入

1）安装

       
       pip 
       
       install 
       
       matplotlib
      
1.

2）导入相关库

Now you don't need to pay attention to what is the exact meaning of the following code,There is a subjective impression can.I will be in a future article,Introduce you don't know which parameters one by one to you.

       
       import 
       
       numpy 
       
       as 
       
       np
       
       import 
       
       pandas 
       
       as 
       
       pd
       
       import 
       
       matplotlib 
       
       as 
       
       mpl
       
       import 
       
       matplotlib.
       
       pyplot 
       
       as 
       
       plt
       
       # 排除警告信息
       
       import 
       
       warnings
       
       warnings.
       
       filterwarnings(
       
       "ignore")
       
       # 打印版本信息
       
       display(
       
       np.
       
       __version__)
       
       display(
       
       pd.
       
       __version__)
       
       display(
       
       mpl.
       
       __version__)
       
       # matplotlibDrawing common parameter Settings
       
       mpl.
       
       rcParams[
       
       "font.family"] 
       
       = 
       
       "SimHei" 
       
       # 设置字体
       
       mpl.
       
       rcParams[
       
       "axes.unicode_minus"]
       
       =
       
       False 
       
       # 用来正常显示负号
       
       plt.
       
       rcParams[
       
       'font.sans-serif']
       
       =[
       
       'SimHei'] 
       
       # 用来正常显示中文标签
       
       # Embedded graphics
       
       %
       
       matplotlib 
       
       inline
      
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6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
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20.
21.

结果如下：

matplotlibThe core principle of drawing on(超详细)_matplotlib_05

3、创建figure(画布)的两种方式

1）Draw a simple line chart

       
       import 
       
       matplotlib 
       
       as 
       
       mpl
       
       import 
       
       matplotlib.
       
       pyplot 
       
       as 
       
       plt
       
       x 
       
       = [
       
       1,
       
       3,
       
       5,
       
       7]
       
       y 
       
       = [
       
       4,
       
       9,
       
       6,
       
       8]
       
       plt.
       
       plot(
       
       x,
       
       y)
       
       plt.
       
       show()
      
1.
2.
3.
4.
5.
6.
7.

结果如下：

matplotlibThe core principle of drawing on(超详细)_matplotlib_06

结果分析：

在前面的叙述中,我们已经说过,想要使用matplotlib绘图,Must first create afigure(画布)对象,然后还要有axes(坐标系).But watch the code,我们并没有创建figure对象,So how can draw？

对于上述疑问,Then we will be creatingfigure(画布)的两种方式.

2）创建figure(画布)的两种方式

隐式创建
显示创建

① 隐式创建figure对象

当第一次执行plt.xxx()The drawing code,系统会去判断是否已经有了figure对象,如果没有,系统会自动创建一个figure对象,并且在这个figure之上,自动创建一个axes坐标系(注意：默认创建一个figure对象,一个axes坐标系).
也就是说,如果我们不设置figure对象,那么一个figure对象上,只能有一个axes坐标系,That we can only draw a shape.

② 隐式创建figureThe problems existing in the object

优势：If we can only draw a small graphics,那么直接使用plt.xxx()的方式,会自动帮我们创建一个figure对象和一个axes坐标系,This graphics eventually is drawn in thisaxesCoordinate system of.

劣势：If we want to be in afigure对象上,绘制多个图形,So we must get eachaxes对象,And then call each positionaxes对象,Can be in the position of each corresponding coordinate system on,进行绘图,如下图所示.注意：如果figureObject is created by default,So we simply can't getaxes对象.因此,We need to show to createfigure对象.

matplotlibThe core principle of drawing on(超详细)_matplotlib绘图原理_07

③ 显示创建figure对象：Future articles will be detailed layout Settings

       
       # 手动创建一个figure对象
       
       figure 
       
       = 
       
       plt.
       
       figure()
       
       # For each locationaxes对象
       
       axes1 
       
       = 
       
       figure.
       
       add_subplot(
       
       2,
       
       1,
       
       1)
       
       axes2 
       
       = 
       
       figure.
       
       add_subplot(
       
       2,
       
       1,
       
       2)
      
1.
2.
3.
4.
5.

如图所示：

matplotlibThe core principle of drawing on(超详细)_坐标轴_08

举例说明：

       
       figure 
       
       = 
       
       plt.
       
       figure()
       
       axes1 
       
       = 
       
       figure.
       
       add_subplot(
       
       2,
       
       1,
       
       1)
       
       axes2 
       
       = 
       
       figure.
       
       add_subplot(
       
       2,
       
       1,
       
       2)
       
       axes1.
       
       plot([
       
       1,
       
       3,
       
       5,
       
       7],[
       
       4,
       
       9,
       
       6,
       
       8])
       
       axes2.
       
       plot([
       
       1,
       
       2,
       
       4,
       
       5],[
       
       8,
       
       4,
       
       6,
       
       2])
       
       figure.
       
       show()
      
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2.
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4.
5.
6.
7.

结果如下：

matplotlibThe core principle of drawing on(超详细)_matplotlib_09

4、The complete drawing steps

① 导库

       
       import 
       
       matplotlib 
       
       as 
       
       mpl
       
       import 
       
       matplotlib.
       
       pyplot 
       
       as
      
1.
2.

② 创建figure画布对象

       
       If draw a simple small graphics,我们可以不设置figure对象,Use the default createdfigure对象,
       
       Of course, we also can display the createfigure对象.
       
       如果一张figure画布上,Need to draw multiple figures.You must show the creation of thefigure对象,然后
       
       Get on each positionaxes对象,To carry on the corresponding position of graphics.
      
1.
2.
3.
4.

③ 根据figureObject to layout Settings

④ 获取对应位置的axes坐标系对象

       
       figure 
       
       = 
       
       plt.
       
       figure()
       
       axes1 
       
       = 
       
       figure.
       
       add_subplot(
       
       2,
       
       1,
       
       1)
       
       axes2 
       
       = 
       
       figure.
       
       add_subplot(
       
       2,
       
       1,
       
       1)
      
1.
2.
3.

⑤ 调用axes对象,进行对应位置的图形绘制

       
       这一步,It is our incoming data,For drawing step.For some details of graphics Settings,In this step can be to.
      
1.

⑥ 显示图形

       
       .
       
       show()
       
       或figure.
       
       show()
      
1.

5、绘图技巧(细节设置)

       
       * 
       
       figure 
       
       画布
       
       * 
       
       axes 
       
       坐标系,一个画布上可以有多个坐标系
       
       * 
       
       axis 
       
       坐标轴,一个坐标系中可以有多个坐标轴,一般都是二维平面坐标系,或者三维立体坐标系
       
       * 
       
       title 
       
       标题
       
       * 
       
       legend 
       
       图例
       
       * 
       
       grid 
       
       背景网格
       
       * 
       
       tick 
       
       刻度
       
       * 
       
       axis 
       
       label 
       
       坐标轴名称
       
       * 
       
       tick 
       
       label 
       
       刻度名称
       
       * 
       
       major 
       
       tick 
       
       label 
       
       主刻度标签
       
       * 
       
       minor 
       
       tick 
       
       label 
       
       副刻度标签
       
       * 
       
       line 
       
       线
       
       * 
       
       style 
       
       线条样式
       
       * 
       
       marker 
       
       点标记
       
       *
      
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通过对matplotlibThe principle of drawing,有所了解之后,We need to learn is commonmatplotlib绘图技巧,Common drawing techniques shown above,These drawing skills can be a good help us draw more beautiful、More intuitive graphics.下一节,I will tellmatplotlib绘图技巧(千万不要错过).

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