Viewing angle control in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the elevation angle after this code runs?

Consider this code that sets the elevation angle of a 3D plot. What will be the elevation angle printed?

Matplotlib

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.view_init(elev=30, azim=45)
elev = ax.elev
print(elev)

A None

B 45

C 0

D 30

💡 Hint

The elev parameter sets the elevation angle in degrees.

The method view_init sets the elevation (elev) and azimuth (azim) angles. Here elev=30 means the elevation angle is 30 degrees.

❓ data_output

intermediate

What is the azimuth angle after setting view_init?

After running this code, what is the azimuth angle stored in ax.azim?

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.view_init(elev=10, azim=120)
azim = ax.azim
print(azim)

A 120

B None

C 0

D 10

💡 Hint

The azim parameter controls the azimuth angle in degrees.

The azim parameter in view_init sets the azimuth angle. Here it is set to 120 degrees.

❓ visualization

advanced

Which option shows the correct azimuth and elevation for this 3D plot?

This code creates a 3D plot and sets the viewing angle. Which option correctly describes the viewing angles used?

Matplotlib

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
import numpy as np
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.linspace(-5, 5, 100)
Y = np.linspace(-5, 5, 100)
X, Y = np.meshgrid(X, Y)
Z = np.sin(np.sqrt(X**2 + Y**2))
ax.plot_surface(X, Y, Z, cmap='viridis')
ax.view_init(elev=60, azim=30)
plt.show()

A Elevation 30°, Azimuth 60°

B Elevation 0°, Azimuth 0°

C Elevation 60°, Azimuth 30°

D Elevation 45°, Azimuth 45°

💡 Hint

Check the parameters passed to view_init(elev=..., azim=...).

The code sets elev=60 and azim=30, so the viewing angle is elevation 60°, azimuth 30°.

🔧 Debug

advanced

What error does this code raise?

This code tries to set the viewing angle but has a mistake. What error will it raise?

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.view_init(elevation=45, azimuth=90)

A TypeError: view_init() got an unexpected keyword argument 'elevation'

B AttributeError: 'Axes3D' object has no attribute 'view_init'

C ValueError: Elevation angle must be between 0 and 90

D No error, runs successfully

💡 Hint

Check the parameter names for view_init method.

The method view_init expects parameters named elev and azim, not elevation or azimuth.

🚀 Application

expert

How to programmatically rotate a 3D plot by 10 degrees azimuth each frame?

You want to create an animation that rotates a 3D plot by increasing the azimuth angle by 10 degrees every frame, starting from 0°. Which code snippet correctly updates the azimuth angle inside a loop?

Matplotlib

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
import numpy as np
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.linspace(-5, 5, 100)
Y = np.linspace(-5, 5, 100)
X, Y = np.meshgrid(X, Y)
Z = np.sin(np.sqrt(X**2 + Y**2))
ax.plot_surface(X, Y, Z, cmap='coolwarm')
for i in range(0, 360, 10):
    # Update viewing angle here
    pass
    plt.pause(0.1)

A ax.view_init(elev=i, azim=30)

B ax.view_init(elev=30, azim=i)

C ax.view_init(elev=0, azim=i*10)

D ax.view_init(elev=30, azim=i*10)

💡 Hint

The azimuth angle changes by i degrees each loop, elevation stays fixed.

To rotate by azimuth angle increasing by 10 degrees each frame, set azim=i and keep elev fixed (e.g., 30).

Practice

1. What does the ax.view_init(elev, azim) function do in matplotlib 3D plots?

easy

A. It sets the vertical and horizontal viewing angles of the 3D plot.

B. It changes the color of the 3D plot.

C. It adds labels to the axes of the 3D plot.

D. It saves the 3D plot as an image file.

Solution

1. Step 1: Understand the function purpose

   The ax.view_init function is used to control the viewing angle of 3D plots in matplotlib.

2. Step 2: Identify parameters meaning

   The parameters elev and azim set the vertical and horizontal angles respectively.

3. Final Answer:

   It sets the vertical and horizontal viewing angles of the 3D plot. -> Option A

4. Quick Check:

   Viewing angle control = ax.view_init(elev, azim) [OK]

Hint: Remember elev = vertical, azim = horizontal angles [OK]

Common Mistakes:

• Confusing view_init with color or label functions
• Mixing up elev and azim parameters
• Thinking it saves the plot instead of changing view

2. Which of the following is the correct syntax to set the elevation to 30 and azimuth to 45 in a matplotlib 3D plot?

easy

A. ax.view_init(azim=30, elev=45)

B. ax.view_init(elev=45, azim=30)

C. ax.view_init(45, 30)

D. ax.view_init(30, 45)

Solution

1. Step 1: Recall parameter order in view_init

   The view_init method takes elev first, then azim.

2. Step 2: Match values to parameters

   Elevation should be 30 and azimuth 45, so ax.view_init(30, 45) is correct.

3. Final Answer:

   ax.view_init(30, 45) -> Option D

4. Quick Check:

   elev=30, azim=45 means ax.view_init(30, 45) [OK]

Hint: Remember order: elev first, then azim [OK]

Common Mistakes:

• Swapping elev and azim values
• Using keyword arguments incorrectly
• Passing azim before elev

3. What will be the effect of this code snippet on the 3D plot's view?

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.view_init(elev=90, azim=0)
plt.show()

medium

A. The plot is viewed from the side at 90 degrees azimuth.

B. The plot is viewed from directly above (top-down view).

C. The plot is viewed from the front with default angles.

D. The plot will raise an error due to invalid angles.

Solution

1. Step 1: Analyze elev=90 effect

   Elevation of 90 degrees means the camera is directly above the plot looking down.

2. Step 2: Analyze azim=0 effect

   Azimuth 0 means no horizontal rotation, so the view is straight down from above.

3. Final Answer:

   The plot is viewed from directly above (top-down view). -> Option B

4. Quick Check:

   elev=90 means top-down view [OK]

Hint: elev=90 means looking straight down [OK]

Common Mistakes:

• Thinking azim=0 changes vertical angle
• Assuming default view instead of top-down
• Believing this causes an error

4. Identify the error in this code that tries to set the viewing angle:

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.view_init(azim=45, elev=30)
plt.show()

medium

A. The projection='3d' is missing in add_subplot.

B. The plt.show() is missing parentheses.

C. The parameters elev and azim are swapped; elev must come first without keywords.

D. There is no error; the code runs correctly.

Solution

1. Step 1: Check parameter usage in view_init

   The view_init method does not accept keyword arguments for elev and azim in this order; it expects positional arguments.

2. Step 2: Identify correct parameter order

   Correct usage is ax.view_init(30, 45) where elev=30 and azim=45 as positional arguments.

3. Final Answer:

   The parameters elev and azim are swapped; elev must come first without keywords. -> Option C

4. Quick Check:

   view_init requires positional elev, azim [OK]

Hint: Use positional args: elev first, azim second [OK]

Common Mistakes:

• Using keyword arguments in wrong order
• Omitting projection='3d' (not the error here)
• Forgetting plt.show() parentheses

5. You want to create a 3D scatter plot and set the view so the plot looks rotated 45 degrees horizontally and tilted 30 degrees vertically. Which code snippet correctly achieves this and also labels the axes?

hard

A. fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.scatter([1,2,3], [4,5,6], [7,8,9])
ax.view_init(30, 45)
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')
ax.set_zlabel('Z axis')
plt.show()

B. fig = plt.figure()
ax = fig.add_subplot(111)
ax.scatter([1,2,3], [4,5,6], [7,8,9])
ax.view_init(45, 30)
plt.show()

C. fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.scatter([1,2,3], [4,5,6], [7,8,9])
ax.view_init(elev=45, azim=30)
plt.show()

D. fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.scatter([1,2,3], [4,5,6], [7,8,9])
ax.view_init(45, 30)
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')
ax.set_zlabel('Z axis')
plt.show()

Solution

1. Step 1: Check subplot creation for 3D

   Only options A, C, and D use projection='3d', which is required for 3D plots.

2. Step 2: Verify view_init parameters

   The question wants elevation 30 and azimuth 45, so ax.view_init(30, 45) is correct. fig = plt.figure() ax = fig.add_subplot(111, projection='3d') ax.scatter([1,2,3], [4,5,6], [7,8,9]) ax.view_init(30, 45) ax.set_xlabel('X axis') ax.set_ylabel('Y axis') ax.set_zlabel('Z axis') plt.show() matches this.

3. Step 3: Confirm axis labels are set

   fig = plt.figure() ax = fig.add_subplot(111, projection='3d') ax.scatter([1,2,3], [4,5,6], [7,8,9]) ax.view_init(30, 45) ax.set_xlabel('X axis') ax.set_ylabel('Y axis') ax.set_zlabel('Z axis') plt.show() sets all three axis labels correctly with set_xlabel, set_ylabel, and set_zlabel.

4. Final Answer:

   Option A correctly sets view angles and labels axes. -> Option A

5. Quick Check:

   3D plot + view_init(30,45) + axis labels = fig = plt.figure() ax = fig.add_subplot(111, projection='3d') ax.scatter([1,2,3], [4,5,6], [7,8,9]) ax.view_init(30, 45) ax.set_xlabel('X axis') ax.set_ylabel('Y axis') ax.set_zlabel('Z axis') plt.show() [OK]

Hint: Use projection='3d', view_init(30,45), then label axes [OK]

Common Mistakes:

• Missing projection='3d' for 3D plots
• Swapping elev and azim values
• Not labeling all three axes