Python Matplotlib library Getting Started Guide, matplotlib Getting Started Guide

Python Matplotlib library Getting Started Guide, matplotlib Getting Started Guide

Introduction to Matplotlib

Matplotlib is a Python toolbox for data visualization in scientific computing. With it, Python can plot a variety of data graphics, such as Matlab and Ave ave. At first, it imitated the Matlab graphical commands, but it was independent of Matlab.
You can use the simple interface in Matplotlib to quickly draw 2D charts.

Matplotlib

The pyplot sub-library in Matplotlib provides plotting APIs similar to matlab.
Copy codeThe Code is as follows:
Import matplotlib. pyplot as plt # import the pyplot sub-database
Plt. figure (figsize = (8, 4) # create a Drawing Object and set the width and height of the object. If you do not create a Drawing Object and call plot directly, Matplotlib will directly create a drawing object.
Plt. plot ([1, 2, 3, 4]) # If the coordinates of y are set to [1, 2, 3, 4], the coordinates of x are [0, 1, 2, 3] drawing in the drawing object. You can set the label, color, and linewidth keyword parameters.
Plt. ylabel ('some numbers ') # Add labels to the Y axis and Add labels to the X axis using xlable
Plt. title ("hello"); # Add a title to the 2D graph
Plt. show () # display 2D images

Basic Drawing

Draw a line chart

Related to the coordinates of the selected point
Copy codeThe Code is as follows:
#-*-Coding: UTF-8 -*-
#! /Usr/bin/env python
Import numpy as np
Import matplotlib. pyplot as plt
X = [0, 1, 2, 4, 5, 6]
Y = [1, 2, 3, 2, 4, 1]
Plt. plot (x, y, '-* R') # dotted line, Star, red
Plt. xlabel ("x-axis ")
Plt. ylabel ("y-axis ")
Plt. show ()

Change the line style to view the plot function parameter settings
Multi-line chart
You only need to input multiple x-y coordinate pairs in the plot function to draw multiple lines.
Copy codeThe Code is as follows:
#-*-Coding: UTF-8 -*-
#! /Usr/bin/env python
Import numpy as np
Import matplotlib. pyplot as plt
X = [0, 1, 2, 4, 5, 6]
Y = [1, 2, 3, 2, 4, 1]
Z = [1, 2, 3, 4, 5, 6]
Plt. plot (x, y, '-- * R', x, z,'-. + G ')
Plt. xlabel ("x-axis ")
Plt. ylabel ("y-axis ")
Plt. title ("hello world ")
Plt. show ()

Bar Chart
Copy codeThe Code is as follows:
#-*-Coding: UTF-8 -*-
#! /Usr/bin/env python
Import numpy as np
Import matplotlib. pyplot as plt
X = [0, 1, 2, 4, 5, 6]
Y = [1, 2, 3, 2, 4, 1]
Z = [1, 2, 3, 4, 5, 6]
Plt. bar (x, y)
Plt. xlabel ("x-axis ")
Plt. ylabel ("y-axis ")
Plt. show ()

Subgraph

The subplot () function specifies the number of numrows, the number of numcols columns, and the number of fignum graphs. The number of graphs cannot exceed the number of rows and the number of columns.
Copy codeThe Code is as follows:
#-*-Coding: UTF-8 -*-
#! /Usr/bin/env python
Import numpy as np
Import matplotlib. pyplot as plt
X = [0, 1, 2, 4, 5, 6]
Y = [1, 2, 3, 2, 4, 1]
Z = [1, 2, 3, 4, 5, 6]
Plt. figure (1)
Plt. subplot (211)
Plt. plot (x, y, '-+ B ')
Plt. subplot (212)
Plt. plot (x, z, '-. * R ')
Plt. show ()

Add text

You need to use the text () function to adjust the price of text on the image, as well as the xlabel (), ylabel (), title () functions.

The text () function returns matplotlib. text. Text.
Copy codeThe Code is as follows:
#-*-Coding: UTF-8 -*-
#! /Usr/bin/env python
Import numpy as np
Import matplotlib. pyplot as plt
X = [0, 1, 2, 4, 5, 6]
Y = [1, 2, 3, 2, 4, 1]
Plt. plot (x, y, '-. * R ')
Plt. text (1, 2, "I'm a text") // The first two parameters represent the text coordinate, and the third parameter is the text to be added
Plt. show ()

Legend Introduction
The legend () function implements the legend function. It has two parameters: the first is the style object, and the second is the description character.
Copy codeThe Code is as follows:
#-*-Coding: UTF-8 -*-
#! /Usr/bin/env python
Import numpy as np
Import matplotlib. pyplot as plt
Line_up, = plt. plot ([1, 2, 3], label = 'line 2 ')
Line_down, = plt. plot ([3, 2, 1], label = 'line 1 ')
Plt. legend (handles = [line_up, line_down])
Plt. show ()

Or call set_label () to add a legend.
Copy codeThe Code is as follows:
#-*-Coding: UTF-8 -*-
#! /Usr/bin/env python
Import numpy as np
Import matplotlib. pyplot as plt
Line, = plt. plot ([1, 2, 3])
Line. set_label ("Label via method ")
Plt. legend ()
Plt. show ()

Add a legend to multiple entries at the same time
Copy codeThe Code is as follows:
#-*-Coding: UTF-8 -*-
#! /Usr/bin/env python
Import numpy as np
Import matplotlib. pyplot as plt
Line1, = plt. plot ([1, 2, 3])
Line2, = plt. plot ([3, 2, 1], '-- B ')
Plt. legend (line1, line2), ('line1', 'line2 '))
Plt. show ()

For more legend settings, refer to the official legend tutorial.