Line colors and width in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

How do you change the color of a line in matplotlib?

You can change the line color by using the color parameter in the plot() function. For example, plt.plot(x, y, color='red') draws a red line.

beginner

What parameter controls the thickness of a line in matplotlib?

The linewidth (or lw) parameter controls the thickness of the line. For example, plt.plot(x, y, linewidth=3) makes the line thicker.

beginner

Can you use color names and hex codes to set line colors in matplotlib?

Yes! You can use named colors like 'blue', 'green', or hex color codes like '#FF5733' to set line colors.

beginner

What is the default line width in matplotlib if you don't specify it?

The default line width is 1.5, which is a thin line.

intermediate

How do you set multiple lines with different colors and widths in one plot?

Call plt.plot() multiple times with different color and linewidth values for each line. For example:
plt.plot(x, y1, color='red', linewidth=2)
plt.plot(x, y2, color='blue', linewidth=4)

Which parameter changes the line thickness in matplotlib?

A linewidth

B color

C linestyle

D marker

The linewidth parameter controls how thick the line appears.

How would you make a green line in matplotlib?

A plt.plot(x, y, linestyle='green')

B plt.plot(x, y, color='green')

C plt.plot(x, y, linewidth='green')

D plt.plot(x, y, marker='green')

The color parameter sets the line color.

What is the default line width if you don't specify it?

A 2.0

B 0.5

C 1.5

D 3.0

Matplotlib uses a default line width of 1.5.

Which of these is a valid way to specify a color in matplotlib?

A '#00FF00'

B 'thick'

C 'dashed'

D 'circle'

Hex color codes like '#00FF00' are valid color specifications.

How do you plot two lines with different colors and widths?

A Use plt.color() and plt.width() functions

B Use one plt.plot() with multiple colors in one string

C Set color and linewidth after plotting

D Call plt.plot() twice with different color and linewidth values

You plot each line separately with its own color and linewidth.

Explain how to change the color and thickness of a line in matplotlib.

Think about the parameters inside plt.plot()

Describe how to plot multiple lines with different colors and widths on the same graph.

Each line needs its own plot call with settings

Practice

1. Which parameter in matplotlib.pyplot.plot() changes the color of the line?

easy

A. linestyle

B. color

C. linewidth

D. marker

Solution

1. Step 1: Understand the purpose of parameters in plot()

   The color parameter sets the line color, while linewidth changes thickness.

2. Step 2: Identify the parameter for color

   Among the options, only color directly changes the line color.

3. Final Answer:

   color -> Option B

4. Quick Check:

   Line color = color [OK]

Hint: Remember: color changes color, linewidth changes thickness [OK]

Common Mistakes:

• Confusing linewidth with color
• Using linestyle to change color
• Trying to use marker for color

2. Which of the following is the correct syntax to set a red line with thickness 3 in matplotlib.pyplot.plot()?

easy

A. plt.plot(x, y, color='red', linewidth=3)

B. plt.plot(x, y, linewidth='red', color=3)

C. plt.plot(x, y, color=3, linewidth='red')

D. plt.plot(x, y, width=3, color='red')

Solution

1. Step 1: Check parameter names and values

   The correct parameters are color with a color string and linewidth with a number.

2. Step 2: Validate plt.plot(x, y, color='red', linewidth=3) syntax

   plt.plot(x, y, color='red', linewidth=3) uses color='red' and linewidth=3, which is correct syntax.

3. Final Answer:

   plt.plot(x, y, color='red', linewidth=3) -> Option A

4. Quick Check:

   Correct parameter names and types = plt.plot(x, y, color='red', linewidth=3) [OK]

Hint: Use color='colorname' and linewidth=number [OK]

Common Mistakes:

• Swapping color and linewidth values
• Using wrong parameter names like width
• Passing numbers as color

3. What will be the color and thickness of the line drawn by this code?

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

medium

A. Blue line with thickness 5

B. Green line with thickness 1

C. Green line with thickness 5

D. Red line with thickness 5

Solution

1. Step 1: Analyze color parameter

   The code sets color='green', so the line color is green.

2. Step 2: Analyze linewidth parameter

   The code sets linewidth=5, so the line thickness is 5 (thicker than default).

3. Final Answer:

   Green line with thickness 5 -> Option C

4. Quick Check:

   color='green' and linewidth=5 = Green line with thickness 5 [OK]

Hint: Check color and linewidth values directly in plot() [OK]

Common Mistakes:

• Ignoring linewidth value
• Assuming default thickness
• Confusing color names

4. Identify the error in this code snippet:

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

medium

A. Missing plt.show() call

B. color should be a number, linewidth should be a string

C. color and linewidth parameters are correct

D. color should be a string, linewidth should be a number

Solution

1. Step 1: Check color parameter type

   color must be a color name string or code, not a number like 5.

2. Step 2: Check linewidth parameter type

   linewidth must be a number (int or float), not a string like 'thick'.

3. Final Answer:

   color should be a string, linewidth should be a number -> Option D

4. Quick Check:

   Parameter types must match expected types [OK]

Hint: color='name', linewidth=number; no numbers for color [OK]

Common Mistakes:

• Passing numbers as color
• Passing strings as linewidth
• Ignoring type errors

5. You want to plot two lines on the same graph: one thick blue line and one thin orange line. Which code correctly does this?

hard

A. plt.plot(x, y1, color='blue', linewidth=6)
plt.plot(x, y2, color='orange', linewidth=1)

B. plt.plot(x, y1, color='orange', linewidth=6)
plt.plot(x, y2, color='blue', linewidth=1)

C. plt.plot(x, y1, linewidth='thick', color='blue')
plt.plot(x, y2, linewidth='thin', color='orange')

D. plt.plot(x, y1, color=6, linewidth='blue')
plt.plot(x, y2, color=1, linewidth='orange')

Solution

1. Step 1: Match colors to lines

   The thick line should be blue, so color='blue' with large linewidth for y1.

2. Step 2: Match thickness and color for second line

   The thin line should be orange, so color='orange' with small linewidth for y2.

3. Step 3: Validate parameter types

   plt.plot(x, y1, color='blue', linewidth=6) plt.plot(x, y2, color='orange', linewidth=1) uses correct parameter names and types for both lines.

4. Final Answer:

   plt.plot(x, y1, color='blue', linewidth=6) plt.plot(x, y2, color='orange', linewidth=1) -> Option A

5. Quick Check:

   Correct colors and linewidths = plt.plot(x, y1, color='blue', linewidth=6) plt.plot(x, y2, color='orange', linewidth=1) [OK]

Hint: Assign color and linewidth clearly for each line [OK]

Common Mistakes:

• Swapping colors and linewidths
• Using strings for linewidth
• Passing numbers as colors