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Practice

Plotting with plt.plot()


The plt.plot() function is the most commonly used method in Matplotlib. It lets you create simple line plots by specifying the data points for the x-axis and y-axis.

If you only pass one list of values, Matplotlib assumes it’s the y-axis and automatically assigns numbers starting from 0 for the x-axis.


Plotting X and Y Values​

When both x and y values are provided, Matplotlib connects the dots with a straight line by default.

Plotting X and Y Values
import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 20, 25, 30, 40]

plt.plot(x, y)
plt.title("Sample Line Plot")
plt.xlabel("X-axis")
plt.ylabel("Y-axis")
plt.show()
  • The order of x and y matters — both lists must be the same length.
  • If the plot looks wrong, check that your data is properly aligned.

Plotting Only Y Values​

You can also plot a list of values without specifying x. In that case, the x-axis will automatically be set to [0, 1, 2, ...].

Plotting Only Y Values
y = [5, 9, 4, 7]

plt.plot(y)
plt.title("Auto X-Axis")
plt.ylabel("Y Values")
plt.show()

This is useful for quick visual checks of any 1D data.


What’s Next?​

Now that you’ve learned how to plot lines using plt.plot(), the next step is to learn how to customize the lines with different colors, markers, and styles.

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