Legend placement and styling in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a legend to the plot.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], label='Line')
plt.[1]()

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

Atitle

Blegend

Cshow

Dxlabel

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.show() instead of plt.legend()

Forgetting to add label in plot() before calling legend()

The legend() function adds a legend to the plot using the labels defined in the plot commands.

2fill in blank

medium

Complete the code to place the legend in the upper left corner.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], label='Line')
plt.legend(loc=[1])
plt.show()

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

A'upper left'

B'upper right'

C'lower left'

D'center'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'upper right' instead of 'upper left'

Not using quotes around the location string

The loc parameter controls the legend position. 'upper left' places it in the top-left corner.

3fill in blank

hard

Fix the error in the code to set the legend font size to 14.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], label='Line')
plt.legend(fontsize=[1])
plt.show()

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

A'14pt'

B'large'

C14

D14.0

Attempts:

3 left

💡 Hint

Common Mistakes

Passing font size as a string with units like '14pt'

Using a float instead of an integer

The fontsize parameter accepts an integer for font size in points, so 14 is correct.

4fill in blank

hard

Fill both blanks to place the legend at center left and set a shadow.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], label='Line')
plt.legend(loc=[1], shadow=[2])
plt.show()

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

A'center left'

B'upper right'

CTrue

DFalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'upper right' instead of 'center left'

Setting shadow to False or a string

Setting loc='center left' places the legend at center left, and shadow=True adds a shadow effect.

5fill in blank

hard

Fill all three blanks to create a legend with a title, placed at the lower center, and with fancy box style.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], label='Line')
plt.legend(title=[1], loc=[2], fancybox=[3])
plt.show()

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

A'My Legend'

B'lower center'

CTrue

DFalse

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the title string

Using incorrect location strings

Setting fancybox to False or a string

The title parameter adds a title to the legend, loc='lower center' places it at the bottom center, and fancybox=True gives the legend a rounded box style.

Practice

1. What does the loc parameter control in a matplotlib legend?

easy

A. The type of plot line used

B. The color of the legend text

C. The size of the plot markers

D. The position of the legend on the plot

Solution

1. Step 1: Understand the role of loc in legend

   The loc parameter specifies where the legend appears on the plot, such as 'upper right' or 'lower left'.

2. Step 2: Differentiate from other styling options

   Other options control color, size, or line style, but loc only controls position.

3. Final Answer:

   The position of the legend on the plot -> Option D

4. Quick Check:

   Legend position = loc [OK]

Hint: Remember: loc means location of legend [OK]

Common Mistakes:

• Confusing loc with color or font size
• Thinking loc changes plot markers
• Assuming loc controls line style

2. Which of the following is the correct syntax to place a legend at the lower left corner in matplotlib?

easy

A. plt.legend(loc='lower left')

B. plt.legend(location='lower left')

C. plt.legend(loc='lower_left')

D. plt.legend(position='lower left')

Solution

1. Step 1: Identify the correct parameter name

   The correct parameter to set legend position is loc, not location or position.

2. Step 2: Use the correct string value

   The valid string is 'lower left' with a space, not 'lower_left' with underscore.

3. Final Answer:

   plt.legend(loc='lower left') -> Option A

4. Quick Check:

   Correct syntax uses loc='lower left' [OK]

Hint: Use loc='lower left' exactly, no underscores [OK]

Common Mistakes:

• Using 'location' instead of 'loc'
• Using underscores instead of spaces
• Using 'position' parameter which doesn't exist

3. What will be the effect of this code snippet?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], label='Line A')
plt.plot([3, 2, 1], label='Line B')
plt.legend(loc='upper center', shadow=True, fontsize='small')
plt.show()

medium

A. Code will raise an error due to invalid fontsize

B. Legend appears at the top center with a shadow and small font

C. Legend appears inside the plot area without shadow

D. Legend appears at the bottom right with default font size

Solution

1. Step 1: Analyze legend parameters

   The loc='upper center' places the legend at the top center. shadow=True adds a shadow behind the legend box. fontsize='small' sets the font size smaller than default.

2. Step 2: Confirm no errors in parameters

   All parameters are valid and supported by matplotlib.

3. Final Answer:

   Legend appears at the top center with a shadow and small font -> Option B

4. Quick Check:

   loc + shadow + fontsize = top center, shadow, small font [OK]

Hint: Check loc for position, shadow=True adds shadow, fontsize sets text size [OK]

Common Mistakes:

• Assuming fontsize='small' causes error
• Confusing loc='upper center' with bottom right
• Ignoring shadow parameter effect

4. Identify the error in this code snippet for legend placement:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], label='A')
plt.plot([3, 2, 1], label='B')
plt.legend(loc='bottomright')
plt.show()

medium

A. plt.legend() must be called before plt.plot()

B. Missing label parameter in plot calls

C. The loc value 'bottomright' is invalid; should be 'lower right'

D. plt.show() is missing parentheses

Solution

1. Step 1: Check the loc parameter value

   The valid location string is 'lower right', not 'bottomright'. 'bottomright' is not recognized by matplotlib.

2. Step 2: Verify other parts of the code

   Labels are correctly set, plt.legend() can be called after plotting, and plt.show() has parentheses.

3. Final Answer:

   The loc value 'bottomright' is invalid; should be 'lower right' -> Option C

4. Quick Check:

   Valid loc strings = 'lower right' not 'bottomright' [OK]

Hint: Use exact loc strings like 'lower right', not 'bottomright' [OK]

Common Mistakes:

• Using invalid loc strings
• Thinking plt.legend() must come before plt.plot()
• Forgetting parentheses in plt.show()

5. You want to place a legend outside the plot on the right side with a title 'Legend', font size 12, and a shadow. Which code snippet achieves this correctly?

hard

A. plt.legend(loc='center right', bbox_to_anchor=(1, 0.5), title='Legend', fontsize='12pt', shadow=True)

B. plt.legend(loc='right side', bbox_to_anchor=(1, 0.5), title='Legend', fontsize=12, shadow=True)

C. plt.legend(loc='center left', bbox_to_anchor=(1, 0.5), title='Legend', fontsize=12, shadow=True)

D. plt.legend(loc='outside right', bbox_to_anchor=(1, 0.5), title='Legend', fontsize=12, shadow=True)

Solution

1. Step 1: Understand placing legend outside plot

   Using loc='center right' with bbox_to_anchor=(1, 0.5) places the legend outside on the right side centered vertically.

2. Step 2: Check styling parameters

   Title 'Legend', font size 12 (string with units '12pt'), and shadow=True are correctly set. loc='right side' and loc='outside right' are invalid.

3. Final Answer:

   plt.legend(loc='center right', bbox_to_anchor=(1, 0.5), title='Legend', fontsize='12pt', shadow=True) -> Option A

4. Quick Check:

   loc + bbox_to_anchor + title + fontsize + shadow = correct legend outside right [OK]

Hint: Use loc='center right' with bbox_to_anchor=(1, 0.5) for outside right legend [OK]

Common Mistakes:

• Using invalid loc like 'right side' or 'outside right'
• Passing fontsize as integer without units
• Forgetting bbox_to_anchor for outside placement