Matplotlib Pyplot

Pyplot is a sub-library of Matplotlib that provides a plotting API similar to MATLAB.

Pyplot is a commonly used plotting module that makes it easy for users to draw 2D charts.

Pyplot contains a series of related plotting functions. Each function makes some modifications to the current image, for example: adding markers to the image, generating a new image, creating a new plotting area in the image, etc.

When using it, we can use import to import the pyplot library and set an aliasplt：

import matplotlib.pyplot as plt

In this way, we can usepltto reference the methods of the Pyplot package.

The following are some commonly used pyplot functions:

plot(): used for drawing line plots and scatter plots
scatter(): used for drawing scatter plots
bar(): used for drawing vertical bar charts and horizontal bar charts
hist(): used for drawing histograms
pie(): used for drawing pie charts
imshow(): used for drawing images
subplots(): used for creating subplots

In addition to these basic functions, pyplot also provides many other functions, such as functions for setting chart properties, functions for adding text and annotations, functions for saving charts to files, and so on.

In the following example, we use two coordinates(0,0)to(6,100)to draw a line:

Example

import matplotlib.pyplot as plt
import numpy as np

xpoints = np.array([0, 6])
ypoints = np.array([0, 100])

plt.plot(xpoints, ypoints)
plt.show()

The output result is as follows:

In the above example, we used Pyplot'splot()function,plot()The function is the most basic function for drawing 2D graphics.

plot()It is used for drawing. It can draw points and lines. The syntax format is as follows:

# 画单条线
plot([x], y, [fmt], *, data=None, **kwargs)
# 画多条线
plot([x], y, [fmt], [x2], y2, [fmt2], ..., **kwargs)

Parameter description:

x, y：The nodes of points or lines, x is the x-axis data, y is the y-axis data. The data can be a list or an array.
fmt：Optional, defines the basic format (such as color, marker, and line style).
**kwargs：Optional, used on 2D plots to set specified properties, such as labels, line width, etc.

>>> plot(x, y) # Create a 2D line plot of the data in y versus the corresponding values in x, using the default style
>>> plot(x, y, 'bo') # Create a 2D line plot of the data in y versus the corresponding values in x, drawn with blue solid circles
>>> plot(y) # x values are 0..N-1
>>> plot(y, 'r+') # Use red + signs

Color characters:'b' blue, 'm' magenta, 'g' green, 'y' yellow, 'r' red, 'k' black, 'w' white, 'c' cyan, '#0053A6' RGB color string. When multiple curves do not specify a color, they will automatically select different colors.

Line style parameters:'-' solid line, '--' dashed line, '-.' dash-dot line, ':' dotted line.

Marker characters:'.' point marker, ',' pixel marker (very small point), 'o' solid circle marker, 'v' inverted triangle marker, '^' upward triangle marker, '>' right triangle marker, '<' left triangle marker... and so on.

If we want to draw a line from coordinates (1, 3) to (8, 10), we need to pass two arrays [1, 8] and [3, 10] toplotfunction:

Example

import matplotlib.pyplot as plt
import numpy as np

xpoints = np.array([1, 8])
ypoints = np.array([3, 10])

plt.plot(xpoints, ypoints)
plt.show()