Basic scatter plot with plt.scatter in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple scatter plot code

What will be the output of this code snippet that uses plt.scatter to plot points?

Matplotlib

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

A An error because plt.scatter requires color argument.

B A line plot connecting points (1,4), (2,5), and (3,6).

C A scatter plot with three points at coordinates (1,4), (2,5), and (3,6) displayed.

D A bar chart with bars at x=1,2,3 and heights 4,5,6.

💡 Hint

Remember, plt.scatter plots points, not lines or bars.

plt.scatter plots individual points at the given x and y coordinates. It does not connect points or create bars.

❓ data_output

intermediate

Number of points plotted by plt.scatter

How many points will be plotted by this code?

Matplotlib

import matplotlib.pyplot as plt
x = [10, 20, 30, 40]
y = [1, 2, 3, 4]
plt.scatter(x, y)
plt.show()

A 4

B 3

C 5

D 0

💡 Hint

Count the number of x or y values given.

There are 4 x values and 4 y values, so 4 points are plotted.

🔧 Debug

advanced

Identify the error in scatter plot code

What error will this code produce?

Matplotlib

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

A ValueError: x and y must be the same size

B TypeError: plt.scatter() missing required positional argument

C No error, plot shows 2 points

D IndexError: list index out of range

💡 Hint

Check if x and y lists have the same length.

plt.scatter requires x and y to have the same number of elements to pair points correctly.

❓ visualization

advanced

Effect of marker size in plt.scatter

What will be the visual difference when running this code compared to default marker size?

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5, 6]
plt.scatter(x, y, s=200)
plt.show()

A Points will appear smaller than default size.

B Code will raise an error due to invalid size argument.

C Points will be connected by lines.

D Points will appear larger than default size.

💡 Hint

The 's' parameter controls marker size in plt.scatter.

Setting s=200 increases the marker size, making points bigger on the plot.

🚀 Application

expert

Plotting two groups with different colors using plt.scatter

Which code correctly plots two groups of points in different colors on the same scatter plot?

A

import matplotlib.pyplot as plt
x1, y1 = [1,2], [3,4]
x2, y2 = [5,6], [7,8]
plt.scatter(x1, y1)
plt.scatter(x2, y2)
plt.show()

B

import matplotlib.pyplot as plt
x1, y1 = [1,2], [3,4]
x2, y2 = [5,6], [7,8]
plt.scatter(x1, y1, color='red')
plt.scatter(x2, y2, color='blue')
plt.show()

C

import matplotlib.pyplot as plt
x = [1,2,5,6]
y = [3,4,7,8]
plt.scatter(x, y, color=['red', 'red', 'blue', 'blue'])
plt.show()

D

import matplotlib.pyplot as plt
x = [1,2,5,6]
y = [3,4,7,8]
plt.scatter(x, y, c='red blue')
plt.show()

💡 Hint

Use separate plt.scatter calls with color argument for each group.

Option B plots two groups separately with specified colors. Option B fails because color list must be a sequence of valid color specs, but matplotlib expects a single color or array of floats for colormap. Option B plots both groups with default color. Option B has invalid color string causing error.