Flash cards
Review the key moves
What is the main idea behind Matplotlib Plotting?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
___ matplotlib.pyplot as pltPut the learning moves in the order that makes the concept easiest to apply.
Plotting x and y points
The plot() function is used to draw points (markers) in a diagram.
By default, the plot() function draws a line from point to point.
The function takes parameters for specifying points in the diagram.
Parameter 1 is an array containing the points on the x-axis .
Parameter 2 is an array containing the points on the y-axis .
If we need to plot a line from (1, 3) to (8, 10), we have to pass two arrays [1, 8] and [3, 10] to the plot function.
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()The x-axis is the horizontal axis.
The y-axis is the vertical axis.
Plotting Without Line
To plot only the markers, you can use shortcut string notation parameter 'o', which means 'rings'.
Example
import matplotlib.pyplot as plt
import numpy as np
xpoints = np.array([1, 8])
ypoints = np.array([3, 10])
plt.plot(xpoints, ypoints, 'o')
plt.show()You will learn more about markers in the next chapter.
Multiple Points
You can plot as many points as you like, just make sure you have the same number of points in both axis.
Example
import matplotlib.pyplot as plt
import numpy as np
xpoints = np.array([1, 2, 6, 8])
ypoints = np.array([3, 8, 1, 10])
plt.plot(xpoints, ypoints)
plt.show()Default X-Points
If we do not specify the points on the x-axis, they will get the default values 0, 1, 2, 3 etc., depending on the length of the y-points.
So, if we take the same example as above, and leave out the x-points, the diagram will look like this:
Example
import matplotlib.pyplot as plt
import numpy as np
ypoints = np.array([3, 8, 1, 10, 5, 7])
plt.plot(ypoints)
plt.show()The x-points in the example above are [0, 1, 2, 3, 4, 5].