Annotation with arrows in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of simple annotation with arrow

What will be the output of this code snippet that creates a plot with an annotation and an arrow?

Matplotlib

import matplotlib.pyplot as plt

plt.plot([1, 2, 3], [4, 5, 6])
plt.annotate('Point 2', xy=(2, 5), xytext=(3, 4), arrowprops=dict(facecolor='blue'))
plt.show()

A A plot with a line connecting points (1,4), (2,5), (3,6) and a blue arrow pointing from (3,4) to (2,5) with label 'Point 2'.

B A plot with a line connecting points (1,4), (2,5), (3,6) and a red arrow pointing from (2,5) to (3,4) with label 'Point 2'.

C A plot with a line connecting points (1,4), (2,5), (3,6) but no arrow or annotation visible.

D A plot with a line connecting points (1,4), (2,5), (3,6) and a blue arrow pointing from (2,5) to (3,4) with label 'Point 2'.

💡 Hint

Remember that xy is the point being annotated and xytext is where the text and arrow start.

The arrow points from the text location (3,4) to the annotated point (2,5). The arrow color is blue as set by facecolor='blue'.

❓ data_output

intermediate

Coordinates of annotated point and text

Given this code, what are the coordinates of the annotated point and the text position?

Matplotlib

import matplotlib.pyplot as plt

plt.plot([0, 1, 2], [0, 1, 4])
plt.annotate('Max', xy=(2, 4), xytext=(1, 3), arrowprops=dict(arrowstyle='->'))
plt.show()

A Annotated point at (2, 4), text at (1, 3)

B Annotated point at (1, 3), text at (2, 4)

C Annotated point at (0, 0), text at (1, 3)

D Annotated point at (2, 4), text at (2, 4)

💡 Hint

xy is the point being annotated, xytext is where the text is placed.

The annotation points to (2,4) and the text is placed at (1,3).

❓ visualization

advanced

Effect of different arrow styles

Which arrow style will produce a simple arrowhead with no tail or fancy shapes?

A 'fancy'

B 'wedge'

C '->'

D '-|>'

💡 Hint

Look for the simplest arrow style name.

The '->' style is a simple arrowhead. Others add tails or shapes.

🔧 Debug

advanced

Identify the error in annotation code

What error will this code raise?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.annotate('Label', xy=(2, 5), xytext=(3, 4), arrowprops=dict(color='red'))
plt.show()

A SyntaxError due to missing colon

B No error, plot shows with red arrow

C ValueError: xy and xytext must be tuples of length 2

D TypeError: 'color' is not a valid key for arrowprops

💡 Hint

Check the valid keys for arrowprops in matplotlib.

The arrowprops dictionary does not accept 'color'. Use 'facecolor' or 'edgecolor' instead.

🚀 Application

expert

Create annotation with curved arrow

Which code snippet correctly creates an annotation with a curved arrow pointing from text at (1, 1) to point (2, 2)?

A plt.annotate('Curved', xy=(1, 1), xytext=(2, 2), arrowprops=dict(arrowstyle='->', connectionstyle='arc3,rad=0.5'))

B plt.annotate('Curved', xy=(2, 2), xytext=(1, 1), arrowprops=dict(arrowstyle='->', connectionstyle='arc3,rad=0.5'))

C plt.annotate('Curved', xy=(2, 2), xytext=(1, 1), arrowprops=dict(arrowstyle='-|>', connectionstyle='arc,rad=0.5'))

D plt.annotate('Curved', xy=(2, 2), xytext=(1, 1), arrowprops=dict(arrowstyle='->', connectionstyle='angle3,rad=0.5'))

💡 Hint

Remember xy is the point being annotated, xytext is text location. Use correct connectionstyle syntax.

Option B correctly sets xy and xytext and uses valid connectionstyle 'arc3,rad=0.5' for a curved arrow.