Line colors and width in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the color of the line in this plot?

Look at the code below that plots a line. What color will the line be?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6], color='green')
plt.show()

A Blue

B Red

C Green

D Black

💡 Hint

The color is set by the 'color' parameter in plt.plot.

The line color is set to 'green' explicitly by the color='green' argument.

❓ Predict Output

intermediate

What is the width of the line plotted?

Check the code below. What is the width of the line shown in the plot?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([0, 1, 2], [2, 3, 4], linewidth=5)
plt.show()

A 5

B 10

C 0.5

D 1 (default width)

💡 Hint

The linewidth parameter controls the thickness of the line.

The linewidth is set to 5 by the linewidth=5 argument.

🔧 Debug

advanced

Why does this code raise an error?

This code tries to plot a red line with width 3 but raises an error. What is the cause?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [3, 2, 1], color='red', linewidth=3)
plt.show()

A linewidth should be line_width, so it's an invalid argument.

B The color value red is not in quotes, causing a NameError.

C plt.plot does not accept color or linewidth arguments.

D The lists for x and y have different lengths.

💡 Hint

String values must be in quotes in Python.

The color argument value red is not quoted, so Python treats it as a variable which is not defined.

❓ data_output

advanced

What is the RGB color code for the line?

The code below plots a line with color='cyan'. What is the RGB tuple for this color?

Matplotlib

import matplotlib.pyplot as plt
line = plt.plot([0, 1], [1, 0], color='cyan')
plt.show()

A (0.0, 1.0, 1.0)

B (1.0, 0.0, 0.0)

C (0.0, 0.0, 1.0)

D (1.0, 1.0, 0.0)

💡 Hint

Cyan is a mix of green and blue at full intensity.

In RGB, cyan is (0, 1, 1) meaning no red, full green, full blue.

🚀 Application

expert

How to plot two lines with different colors and widths?

You want to plot two lines on the same graph: one red line with width 2, and one blue line with width 4. Which code does this correctly?

A

import matplotlib.pyplot as plt
plt.plot([1,2,3], [3,2,1], color='red', linewidth=2)
plt.plot([1,2,3], [1,2,3], color='blue', linewidth=4)
plt.show()

B

import matplotlib.pyplot as plt
plt.plot([1,2,3], [3,2,1], 'red', 2)
plt.plot([1,2,3], [1,2,3], 'blue', 4)
plt.show()

C

import matplotlib.pyplot as plt
plt.plot([1,2,3], [3,2,1], color='red', width=2)
plt.plot([1,2,3], [1,2,3], color='blue', width=4)
plt.show()

D

import matplotlib.pyplot as plt
plt.plot([1,2,3], [3,2,1], c='red', linewidth=2)
plt.plot([1,2,3], [1,2,3], c='blue', linewidth=4)
plt.show()

💡 Hint

Use color= and linewidth= parameters correctly.

Options A and D use correct parameter names and values ('color' or its alias 'c'). Option B passes positional arguments incorrectly. Option C uses 'width' which is invalid.