Axes creation with add_subplot in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a subplot in a figure.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.[1](111)
plt.show()

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

Asubplot

Badd_subplot

Caddplot

Dplot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'subplot' instead of 'add_subplot' on the figure object.

Using 'plot' which is for plotting data, not creating axes.

The add_subplot method adds a subplot to the figure. The code 111 means 1 row, 1 column, first subplot.

2fill in blank

medium

Complete the code to create a 2x2 grid of subplots and select the second subplot.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot([1])
plt.show()

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

A222

B212

C122

D221

Attempts:

3 left

💡 Hint

Common Mistakes

Using '221' which selects the first subplot.

Using '212' which is 2 rows, 1 column, 2nd subplot.

The code 222 means 2 rows, 2 columns, and select the 2nd subplot.

3fill in blank

hard

Fix the error in the code to correctly add a subplot to the figure.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.[1](1, 2, 1)
plt.show()

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

Aadd_subplot

Bsubplot

Caddplot

Dplot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'subplot' which is a pyplot function, not a figure method.

Using 'addplot' which does not exist.

The add_subplot method accepts three separate arguments for rows, columns, and index.

4fill in blank

hard

Fill both blanks to create a 3x1 grid and select the second subplot.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.[1]([2])
plt.show()

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

Aadd_subplot

B312

C311

Dsubplot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'subplot' instead of 'add_subplot'.

Using '311' which selects the first subplot.

Use add_subplot method with code 312 for 3 rows, 1 column, 2nd subplot.

5fill in blank

hard

Fill all three blanks to create a 2x3 grid and select the fourth subplot.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.[1]([2], [3], 4)
plt.show()

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

Aadd_subplot

B2

C3

Dsubplot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'subplot' instead of 'add_subplot'.

Swapping rows and columns arguments.

The add_subplot method takes rows, columns, and index as separate arguments. Here, 2 rows, 3 columns, and 4th subplot.

Practice

1. What does the add_subplot method do in matplotlib?

easy

A. It removes a plot from the figure.

B. It saves the figure to a file.

C. It changes the color of the plot.

D. It adds a new plot (axes) to an existing figure.

Solution

1. Step 1: Understand the purpose of add_subplot

   The add_subplot method is used to add one or more plots (axes) inside a figure in matplotlib.

2. Step 2: Compare with other options

   Saving, coloring, or removing plots are done by other methods, not add_subplot.

3. Final Answer:

   It adds a new plot (axes) to an existing figure. -> Option D

4. Quick Check:

   add_subplot adds axes [OK]

Hint: Remember: add_subplot adds plots inside a figure [OK]

Common Mistakes:

• Confusing add_subplot with savefig
• Thinking it changes plot colors
• Assuming it deletes plots

2. Which of the following is the correct way to create a 2x2 grid of subplots and select the third subplot using add_subplot?

easy

A. fig.add_subplot(2, 2, 3)

B. fig.add_subplot(3, 2, 2)

C. fig.add_subplot(2, 3, 1)

D. fig.add_subplot(2, 2)

Solution

1. Step 1: Understand the parameters of add_subplot

   The method add_subplot(rows, columns, index) creates a grid and selects the subplot at the given index.

2. Step 2: Match the correct grid and index

   For a 2x2 grid, the third subplot is at position 3, so fig.add_subplot(2, 2, 3) is correct.

3. Final Answer:

   fig.add_subplot(2, 2, 3) -> Option A

4. Quick Check:

   2x2 grid, third subplot = add_subplot(2,2,3) [OK]

Hint: Use (rows, cols, position) to pick subplot [OK]

Common Mistakes:

• Mixing rows and columns order
• Omitting the position argument
• Using wrong grid size

3. What will be the output of the following code snippet?

import matplotlib.pyplot as plt
fig = plt.figure()
ax1 = fig.add_subplot(121)
ax2 = fig.add_subplot(122)
print(type(ax1), type(ax2))

medium

A.

B.

C.

D. SyntaxError

Solution

1. Step 1: Understand add_subplot with 3-digit code

   The code 121 means 1 row, 2 columns, subplot 1; 122 means subplot 2.

2. Step 2: Check the returned object types

   Both ax1 and ax2 are subplot axes objects of type AxesSubplot.

3. Final Answer:

   <class 'matplotlib.axes._subplots.AxesSubplot'> <class 'matplotlib.axes._subplots.AxesSubplot'> -> Option A

4. Quick Check:

   add_subplot returns AxesSubplot objects [OK]

Hint: 3-digit code means (rows, cols, index) [OK]

Common Mistakes:

• Expecting Figure type instead of Axes
• Confusing syntax with tuple input
• Thinking it causes syntax error

4. Identify the error in this code snippet:

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(2, 2)
ax.plot([1, 2, 3], [4, 5, 6])
plt.show()

medium

A. plt.figure() should be plt.subplots() instead.

B. Missing the subplot position argument in add_subplot.

C. The plot data lists have different lengths.

D. plt.show() is called before plotting.

Solution

1. Step 1: Check add_subplot parameters

   The method requires three arguments: rows, columns, and position. Here, only two are given.

2. Step 2: Verify other parts of the code

   Plot data lists have equal length, plt.show() is correctly placed, and plt.figure() is valid.

3. Final Answer:

   Missing the subplot position argument in add_subplot. -> Option B

4. Quick Check:

   add_subplot needs 3 args (rows, cols, pos) [OK]

Hint: add_subplot needs three numbers: rows, cols, position [OK]

Common Mistakes:

• Forgetting the position argument
• Confusing plt.figure() with plt.subplots()
• Assuming plt.show() order matters here

5. You want to create a figure with 3 subplots arranged in 1 row and 3 columns. You want to add the second subplot and plot a line on it. Which code snippet correctly does this?

hard

A. fig = plt.figure()
ax = fig.add_subplot(3, 1, 2)
ax.plot([0, 1, 2], [2, 1, 0])
plt.show()

B. fig, ax = plt.subplots(3, 1)
ax[1].plot([0, 1, 2], [2, 1, 0])
plt.show()

C. fig = plt.figure()
ax = fig.add_subplot(1, 3, 2)
ax.plot([0, 1, 2], [2, 1, 0])
plt.show()

D. fig = plt.figure()
ax = fig.add_subplot(1, 2, 3)
ax.plot([0, 1, 2], [2, 1, 0])
plt.show()

Solution

1. Step 1: Understand subplot layout

   We want 1 row and 3 columns, so the call is add_subplot(1, 3, position).

2. Step 2: Select the second subplot and plot

   Position 2 selects the second subplot. The plot command is correct.

3. Step 3: Check other options

   fig, ax = plt.subplots(3, 1) ax[1].plot([0, 1, 2], [2, 1, 0]) plt.show() uses plt.subplots with wrong shape, C uses wrong layout, D uses invalid position 3 in 1x2 grid.

4. Final Answer:

   fig = plt.figure() ax = fig.add_subplot(1, 3, 2) ax.plot([0, 1, 2], [2, 1, 0]) plt.show() -> Option C

5. Quick Check:

   1 row, 3 cols, second subplot = add_subplot(1,3,2) [OK]

Hint: Match rows, cols, and position carefully [OK]

Common Mistakes:

• Mixing rows and columns numbers
• Using wrong subplot index
• Confusing plt.figure() and plt.subplots()