Bar chart color customization in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the color of the bars to blue.

Matplotlib

import matplotlib.pyplot as plt

values = [3, 7, 5]
plt.bar([1, 2, 3], values, color=[1])
plt.show()

Drag options to blanks, or click blank then click option'

A'green'

B'red'

C'blue'

D'yellow'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the quotes around the color name.

Using a color name not recognized by matplotlib.

The color parameter sets the color of the bars. Here, 'blue' colors all bars blue.

2fill in blank

medium

Complete the code to set different colors for each bar using a list.

Matplotlib

import matplotlib.pyplot as plt

values = [4, 6, 8]
colors = ['red', 'green', 'blue']
plt.bar([1, 2, 3], values, color=[1])
plt.show()

Drag options to blanks, or click blank then click option'

A[1, 2, 3]

Bcolors

Cvalues

D'red'

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a single color string instead of a list.

Passing the values list instead of colors.

Passing a list of colors to color colors each bar differently.

3fill in blank

hard

Fix the error in the code to correctly set the bar colors using a dictionary.

Matplotlib

import matplotlib.pyplot as plt

values = [5, 3, 9]
color_map = {1: 'cyan', 2: 'magenta', 3: 'yellow'}
colors = [color_map[i] for i in [1, 2, 3]]
plt.bar([1, 2, 3], values, color=[1])
plt.show()

Drag options to blanks, or click blank then click option'

Acolors

B[color_map]

Ccolor_map

Dvalues

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the dictionary color_map directly causes an error.

Passing the values list instead of colors.

The colors list contains the colors for each bar, so it should be passed to color.

4fill in blank

hard

Fill both blanks to create a bar chart with bars colored red if value > 5, else green.

Matplotlib

import matplotlib.pyplot as plt

values = [2, 7, 4, 9]
colors = ['red' if value [1] 5 else [2] for value in values]
plt.bar(range(len(values)), values, color=colors)
plt.show()

Drag options to blanks, or click blank then click option'

A>

B<

C'green'

D'blue'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong comparison operator.

Forgetting quotes around the color names.

The condition checks if each value is greater than 5 to assign 'red', otherwise 'green'.

5fill in blank

hard

Fill all three blanks to create a dictionary of bar heights squared for bars with height > 3, using uppercase keys.

Matplotlib

values = {'a': 2, 'b': 5, 'c': 7}
squares = [1]: [2]**2 for [3] in values if values[[3]] > 3

Drag options to blanks, or click blank then click option'

Ak.upper()

Bvalues[k]

Ck

Dv

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable names.

Not converting keys to uppercase.

This dictionary comprehension creates keys as uppercase letters and values as squares of the original values greater than 3.

Practice

1. What does the color parameter do in the plt.bar() function in matplotlib?

easy

A. It changes the color of the bars in the bar chart.

B. It changes the size of the bars.

C. It adds labels to the bars.

D. It changes the style of the axes.

Solution

1. Step 1: Understand the role of plt.bar()

   The plt.bar() function draws bars for a bar chart.

2. Step 2: Identify the color parameter effect

   The color parameter sets the color of the bars, either one color for all or a list for each bar.

3. Final Answer:

   It changes the color of the bars in the bar chart. -> Option A

4. Quick Check:

   color changes bar colors [OK]

Hint: Remember: color = bar colors in plt.bar() [OK]

Common Mistakes:

• Confusing color with size or labels
• Thinking color changes axes or grid
• Using color parameter outside plt.bar()

2. Which of the following is the correct syntax to set all bars to blue in a bar chart using matplotlib?

easy

A. plt.bar(x, height, bar_color='blue')

B. plt.bar(x, height, color='blue')

C. plt.bar(x, height, col='blue')

D. plt.bar(x, height, colors='blue')

Solution

1. Step 1: Recall the correct parameter name

   The parameter to set bar colors is color, not colors, col, or bar_color.

2. Step 2: Check the syntax for setting a single color

   Using color='blue' applies blue color to all bars.

3. Final Answer:

   plt.bar(x, height, color='blue') -> Option B

4. Quick Check:

   Use color parameter exactly [OK]

Hint: Use exact parameter name: color='colorname' [OK]

Common Mistakes:

• Using 'colors' instead of 'color'
• Using 'col' or 'bar_color' which are invalid
• Misspelling 'color' parameter

3. What will be the color of each bar in the following code?

import matplotlib.pyplot as plt
x = [1, 2, 3]
height = [4, 5, 6]
colors = ['red', 'green', 'blue']
plt.bar(x, height, color=colors)
plt.show()

medium

A. Bars will be red, green, and blue respectively.

B. Bars will be blue, green, and red respectively.

C. All bars will be red.

D. The code will cause an error.

Solution

1. Step 1: Understand color list usage in plt.bar()

   When a list of colors is passed to color, each bar gets the corresponding color in order.

2. Step 2: Match colors to bars

   Bars at x=1,2,3 get colors 'red', 'green', 'blue' respectively.

3. Final Answer:

   Bars will be red, green, and blue respectively. -> Option A

4. Quick Check:

   List of colors assigns colors in order [OK]

Hint: List colors in order to color bars individually [OK]

Common Mistakes:

• Assuming all bars get first color only
• Mixing order of colors
• Expecting error from list input

4. Identify the error in this code snippet that tries to color bars individually:

import matplotlib.pyplot as plt
x = [1, 2, 3]
height = [4, 5, 6]
colors = ['red', 'green']
plt.bar(x, height, color=colors)
plt.show()

medium

A. The colors list has fewer colors than bars, causing an error.

B. The colors list should be a tuple, not a list.

C. There is no error; the code runs fine.

D. The color parameter should be named colors.

Solution

1. Step 1: Check length of colors list vs bars

   There are 3 bars but only 2 colors provided.

2. Step 2: Understand matplotlib behavior

   Matplotlib allows a shorter list of colors and cycles through them to color bars.

3. Final Answer:

   There is no error; the code runs fine. -> Option C

4. Quick Check:

   Colors list cycles if shorter than bars [OK]

Hint: Matplotlib cycles colors if list shorter than bars [OK]

Common Mistakes:

• Using fewer colors than bars
• Wrong parameter name 'colors'
• Assuming matplotlib throws error on shorter color list

5. You want to create a bar chart with 5 bars where bars at even positions are blue and odd positions are orange. Which code correctly customizes the bar colors?

hard

A. colors = ['blue', 'orange', 'blue', 'orange', 'blue']
plt.bar(x, height, color=colors)

B. colors = ['blue', 'blue', 'orange', 'orange', 'blue']
plt.bar(x, height, color=colors)

C. colors = ['orange', 'orange', 'blue', 'blue', 'orange']
plt.bar(x, height, color=colors)

D. colors = ['orange', 'blue', 'orange', 'blue', 'orange']
plt.bar(x, height, color=colors)

Solution

1. Step 1: Identify bar positions and colors

   Positions: 1 (odd), 2 (even), 3 (odd), 4 (even), 5 (odd). Odd bars = orange, even bars = blue.

2. Step 2: Map colors to positions in list

   List must be ['orange', 'blue', 'orange', 'blue', 'orange'] to match positions.

3. Final Answer:

   colors = ['orange', 'blue', 'orange', 'blue', 'orange'] plt.bar(x, height, color=colors) -> Option D

4. Quick Check:

   Color list matches odd/even bar positions [OK]

Hint: Assign colors by position index for pattern [OK]

Common Mistakes:

• Swapping colors for odd/even positions
• Using wrong order in colors list
• Not matching list length to bars