Marker size variation in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the marker size to 100 in the scatter plot.

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5, 6]
plt.scatter(x, y, s=[1])
plt.show()

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

A100

B1

C10

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'size' instead of 's' parameter.

Setting s to a very small number like 1 which makes markers hard to see.

The 's' parameter in plt.scatter controls the marker size. Setting s=100 makes the markers larger.

2fill in blank

medium

Complete the code to create a scatter plot with marker sizes varying by the values in the list 'sizes'.

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [10, 20, 25, 30]
sizes = [20, 50, 80, 200]
plt.scatter(x, y, s=[1])
plt.show()

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

Ay

Bx

Csizes

D[10, 20, 30, 40]

Attempts:

3 left

💡 Hint

Common Mistakes

Passing x or y instead of sizes to the 's' parameter.

Passing a list of wrong length to 's'.

Passing the list 'sizes' to the 's' parameter sets marker sizes individually for each point.

3fill in blank

hard

Fix the error in the code to correctly vary marker sizes using the 'sizes' list.

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5, 6]
sizes = [30, 60, 90]
plt.scatter(x, y, s=[1])
plt.show()

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

Asizes

Bsize

C[30, 60, 90]

Ds

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'size' instead of 's' parameter.

Passing a string instead of the variable.

The 's' parameter must be assigned the variable 'sizes' to vary marker sizes correctly.

4fill in blank

hard

Fill both blanks to create a scatter plot with marker sizes scaled by 10 times the values in 'data_sizes'.

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [5, 6, 7, 8]
data_sizes = [2, 4, 6, 8]
scaled_sizes = [[1] * size for size in data_sizes]
plt.scatter(x, y, s=[2])
plt.show()

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A10

Bdata_sizes

Cscaled_sizes

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Passing data_sizes directly without scaling.

Using wrong variable names.

Multiply each size by 10 to scale, then pass the scaled_sizes list to 's' for marker sizes.

5fill in blank

hard

Fill all three blanks to create a scatter plot with marker sizes as the square of x values and color as y values.

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [10, 20, 30, 40]
sizes = [[1] for val in x]
plt.scatter(x, y, s=sizes, c=[2], cmap=[3])
plt.colorbar()
plt.show()

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Aval**2

By

C'viridis'

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using x instead of y for colors.

Not squaring x values for sizes.

Using invalid colormap name.

Marker sizes are squares of x values, colors are y values, and 'viridis' colormap is used.

Practice

1. What does the s parameter control in the plt.scatter() function in matplotlib?

easy

A. The size of the markers in the scatter plot

B. The color of the markers

C. The shape of the markers

D. The transparency of the markers

Solution

1. Step 1: Understand the role of plt.scatter()

   The plt.scatter() function creates scatter plots where each point can have different visual properties.

2. Step 2: Identify the s parameter purpose

   The s parameter specifically sets the size of each marker in the scatter plot, either as a single value or a list of sizes.

3. Final Answer:

   The size of the markers in the scatter plot -> Option A

4. Quick Check:

   s controls marker size [OK]

Hint: Remember: 's' stands for size in scatter plots [OK]

Common Mistakes:

• Confusing 's' with color or shape parameters
• Thinking 's' controls transparency
• Assuming 's' changes marker style

2. Which of the following is the correct way to set marker sizes to 50 for all points in a scatter plot using matplotlib?

easy

A. plt.scatter(x, y, size=50)

B. plt.scatter(x, y, s=50)

C. plt.scatter(x, y, marker_size=50)

D. plt.scatter(x, y, sizes=50)

Solution

1. Step 1: Recall the parameter name for marker size

   The correct parameter to set marker size in plt.scatter() is s.

2. Step 2: Check the syntax for setting size

   Using s=50 sets all markers to size 50. Other options use incorrect parameter names.

3. Final Answer:

   plt.scatter(x, y, s=50) -> Option B

4. Quick Check:

   Use s for size [OK]

Hint: Use s to set size, not 'size' or 'sizes' [OK]

Common Mistakes:

• Using 'size' or 'sizes' instead of 's'
• Trying to set marker size with 'marker_size'
• Syntax errors from wrong parameter names

3. What will be the output marker sizes for the scatter plot from this code?

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5, 6]
sizes = [20, 50, 80]
plt.scatter(x, y, s=sizes)
plt.show()

medium

A. All markers will have size 20

B. Code will raise an error due to wrong size input

C. Markers will have default size because list is invalid

D. Markers will have sizes 20, 50, and 80 respectively

Solution

1. Step 1: Understand s with list input

   The s parameter accepts a list to assign different sizes to each marker.

2. Step 2: Match sizes to points

   Since sizes = [20, 50, 80], the first point gets size 20, second 50, third 80.

3. Final Answer:

   Markers will have sizes 20, 50, and 80 respectively -> Option D

4. Quick Check:

   List in s sets sizes per point [OK]

Hint: List in s sets sizes point-wise [OK]

Common Mistakes:

• Assuming all markers get the first size
• Thinking list input causes error
• Confusing s with color list

4. Identify the error in this code snippet that tries to vary marker sizes:

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5, 6]
sizes = [30, 60]
plt.scatter(x, y, s=sizes)
plt.show()

medium

A. The plt.scatter function is misspelled

B. The s parameter cannot accept lists

C. The sizes list length does not match x and y length

D. The variable sizes is not defined

Solution

1. Step 1: Check lengths of data and sizes

   The x and y lists have 3 points, but sizes list has only 2 values.

2. Step 2: Understand size list requirement

   The s list must match the number of points; otherwise, matplotlib raises a ValueError.

3. Final Answer:

   The sizes list length does not match x and y length -> Option C

4. Quick Check:

   Sizes list length must equal data points [OK]

Hint: Match sizes list length to data points [OK]

Common Mistakes:

• Ignoring size list length mismatch
• Thinking s can't be a list
• Assuming matplotlib auto-fills missing sizes

5. You want to create a scatter plot where marker sizes represent the population of cities. Given:

cities = ['A', 'B', 'C']
population = [1000, 5000, 3000]
x = [1, 2, 3]
y = [4, 5, 6]

Which code correctly scales the population to marker sizes and plots them?

hard

A. plt.scatter(x, y, s=[p*10 for p in population])

B. plt.scatter(x, y, s=[p/10 for p in population])

C. plt.scatter(x, y, s=population)

D. plt.scatter(x, y, s=[p**2 for p in population])

Solution

1. Step 1: Understand marker size scaling

   Population values are large; directly using them as sizes will create huge markers.

2. Step 2: Choose appropriate scaling

   Multiplying population by 10 scales sizes visibly but keeps them reasonable. Dividing by 10 makes markers too small; squaring makes them too large.

3. Final Answer:

   plt.scatter(x, y, s=[p*10 for p in population]) -> Option A

4. Quick Check:

   Scale sizes for visibility using multiplication [OK]

Hint: Scale data to reasonable marker sizes by multiplying [OK]

Common Mistakes:

• Using raw large values causing huge markers
• Dividing sizes too much making markers tiny
• Using squared sizes causing disproportionate markers