3D wireframe plots in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the 3D plotting toolkit from matplotlib.

Matplotlib

from mpl_toolkits.mplot3d import [1]

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

Awireframe3d

Bplot3d

CAxes3D

Dplot_wireframe

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to import a function instead of the class.

Using a non-existent module name.

The Axes3D class is needed to create 3D plots in matplotlib.

2fill in blank

medium

Complete the code to create a 3D subplot in matplotlib.

Matplotlib

fig = plt.figure()
ax = fig.add_subplot(111, projection='[1]')

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

A3d

B2d

C3D

Dwireframe

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase '3D' instead of lowercase '3d'.

Using '2d' projection which creates a 2D plot.

The projection must be set to '3d' (all lowercase) to create a 3D plot.

3fill in blank

hard

Fix the error in the code to plot a 3D wireframe using X, Y, Z data.

Matplotlib

ax.[1](X, Y, Z)

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

Aplot_wireframe

Bwireframe_plot

Cplot3d_wireframe

Dwireframe3d

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent method name.

Mixing method names from other plotting libraries.

The correct method to create a 3D wireframe plot is plot_wireframe.

4fill in blank

hard

Fill both blanks to create meshgrid arrays for X and Y from 1D arrays x and y.

Matplotlib

X, Y = np.[1](x, y, [2]='xy')

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

Ameshgrid

Blinspace

Cindexing

Darange

Attempts:

3 left

💡 Hint

Common Mistakes

Using linspace or arange instead of meshgrid.

Confusing parameter names.

np.meshgrid creates coordinate matrices from coordinate vectors. The indexing parameter controls the indexing style.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps each word to its length if length is greater than 3.

Matplotlib

result = { [1]: [2] for [3] in words if len([3]) > 3 }

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

Aword

Blen(word)

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Using the word itself as the value instead of its length.

The dictionary comprehension uses word as the key and len(word) as the value, iterating over word in words.

Practice

1. What does a 3D wireframe plot in matplotlib primarily show?

easy

A. Only the color distribution of data points

B. A flat 2D scatter plot

C. The shape of data or functions in three dimensions using lines

D. A pie chart with 3D effects

Solution

1. Step 1: Understand the purpose of 3D wireframe plots

   3D wireframe plots use a grid of lines to represent the shape of data or functions in three dimensions.

2. Step 2: Compare with other plot types

   Unlike scatter or pie charts, wireframe plots focus on the surface structure, not just colors or flat points.

3. Final Answer:

   The shape of data or functions in three dimensions using lines -> Option C

4. Quick Check:

   3D wireframe = 3D shape with lines [OK]

Hint: Wireframe plots show 3D shapes with lines, not colors or points [OK]

Common Mistakes:

• Confusing wireframe with scatter or surface plots
• Thinking wireframe shows only colors
• Assuming wireframe is 2D

2. Which of the following is the correct way to create a 3D wireframe plot using matplotlib?

easy

A. ax.plot_wireframe(X, Y, Z)

B. ax.plot_surface(X, Y, Z)

C. plt.plot_wireframe(X, Y, Z)

D. ax.scatter_wireframe(X, Y, Z)

Solution

1. Step 1: Identify the correct method for wireframe plots

   The method plot_wireframe is called on the 3D axes object ax.

2. Step 2: Eliminate incorrect options

   plot_surface creates a surface plot, not wireframe. plt.plot_wireframe is invalid because plt does not have this method. scatter_wireframe does not exist.

3. Final Answer:

   ax.plot_wireframe(X, Y, Z) -> Option A

4. Quick Check:

   Wireframe method is plot_wireframe on ax [OK]

Hint: Use ax.plot_wireframe for 3D wireframe plots [OK]

Common Mistakes:

• Calling plot_wireframe on plt instead of ax
• Using plot_surface instead of plot_wireframe
• Using non-existent methods like scatter_wireframe

3. What will the following code output?

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.arange(-5, 6, 5)
Y = np.arange(-5, 6, 5)
X, Y = np.meshgrid(X, Y)
Z = X**2 - Y**2
ax.plot_wireframe(X, Y, Z, rstride=1, cstride=1)
plt.show()

medium

A. A 3D wireframe plot showing a saddle shape

B. A 2D line plot of X and Y

C. A scatter plot of points

D. An error due to incorrect meshgrid usage

Solution

1. Step 1: Understand the meshgrid and function

   X and Y create a grid from -5 to 5 with step 5, so points at -5, 0, 5. Z = X^2 - Y^2 forms a saddle shape.

2. Step 2: Analyze the plot_wireframe call

   Using rstride=1 and cstride=1 plots all grid lines, producing a wireframe of the saddle surface.

3. Final Answer:

   A 3D wireframe plot showing a saddle shape -> Option A

4. Quick Check:

   Wireframe of Z = X^2 - Y^2 = saddle shape [OK]

Hint: Z = X² - Y² creates a saddle; wireframe shows surface shape [OK]

Common Mistakes:

• Thinking meshgrid creates error
• Confusing wireframe with scatter or 2D plot
• Ignoring the shape of Z function

4. Identify the error in this code snippet for a 3D wireframe plot:

import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.linspace(-3, 3, 10)
Y = np.linspace(-3, 3, 10)
Z = np.sin(X) * np.cos(Y)
ax.plot_wireframe(X, Y, Z)
plt.show()

medium

A. X and Y should be lists, not arrays

B. Missing import for Axes3D

C. plot_wireframe does not exist

D. Z is not a 2D array matching X and Y meshgrid shape

Solution

1. Step 1: Check shapes of X, Y, and Z

   X and Y are 1D arrays; Z is computed element-wise but is also 1D, not 2D grid.

2. Step 2: Understand plot_wireframe requirements

   plot_wireframe requires X, Y, Z to be 2D arrays from meshgrid to plot a surface grid.

3. Final Answer:

   Z is not a 2D array matching X and Y meshgrid shape -> Option D

4. Quick Check:

   plot_wireframe needs 2D X, Y, Z arrays [OK]

Hint: Use meshgrid to make X, Y, Z 2D arrays for wireframe [OK]

Common Mistakes:

• Passing 1D arrays instead of meshgrid 2D arrays
• Ignoring shape mismatch errors
• Assuming plot_wireframe works with 1D inputs

5. You want to plot a 3D wireframe of the function Z = sin(sqrt(X² + Y²)) over the range -6 to 6 for both X and Y with a grid spacing of 0.5. Which code snippet correctly creates this plot with a blue wireframe and stride of 5?

hard

A. import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.linspace(-6, 6, 25)
Y = np.linspace(-6, 6, 25)
Z = np.sin(np.sqrt(X**2 + Y**2))
ax.plot_wireframe(X, Y, Z, color='blue', stride=5)
plt.show()

B. import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.arange(-6, 6.5, 0.5)
Y = np.arange(-6, 6.5, 0.5)
X, Y = np.meshgrid(X, Y)
R = np.sqrt(X**2 + Y**2)
Z = np.sin(R)
ax.plot_wireframe(X, Y, Z, rstride=5, cstride=5, color='blue')
plt.show()

C. import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.arange(-6, 6, 0.5)
Y = np.arange(-6, 6, 0.5)
X, Y = np.meshgrid(X, Y)
Z = np.sin(np.sqrt(X**2 + Y**2))
ax.plot_wireframe(X, Y, Z, rstride=5, cstride=5, color='red')
plt.show()

D. import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.arange(-6, 6, 0.5)
Y = np.arange(-6, 6, 0.5)
X, Y = np.meshgrid(X, Y)
Z = np.sin(np.sqrt(X**2 + Y**2))
ax.plot_wireframe(X, Y, Z, rstride=0.5, cstride=0.5, color='blue')
plt.show()

Solution

1. Step 1: Create X and Y grids with correct range and spacing

   Using np.arange(-6, 6.5, 0.5) ensures points from -6 to 6 with 0.5 spacing. Then meshgrid creates 2D arrays.

2. Step 2: Calculate Z and plot with correct stride and color

   Z is computed as sin(sqrt(X² + Y²)). The wireframe uses rstride=5 and cstride=5 for spacing lines, and color='blue' for blue lines.

3. Final Answer:

   Code snippet A correctly creates the desired 3D wireframe plot -> Option B

4. Quick Check:

   Correct meshgrid, stride=5, color='blue' = import numpy as np import matplotlib.pyplot as plt fig = plt.figure() ax = fig.add_subplot(111, projection='3d') X = np.arange(-6, 6.5, 0.5) Y = np.arange(-6, 6.5, 0.5) X, Y = np.meshgrid(X, Y) R = np.sqrt(X**2 + Y**2) Z = np.sin(R) ax.plot_wireframe(X, Y, Z, rstride=5, cstride=5, color='blue') plt.show() [OK]

Hint: Use meshgrid, rstride/cstride for spacing, color param for wireframe [OK]

Common Mistakes:

• Using stride instead of rstride and cstride
• Incorrect range or missing meshgrid
• Wrong color or stride values