Scatter plots in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Basic Scatter Plot Command

What will be the output of the following MATLAB code snippet?

MATLAB

x = 1:5;
y = [2 4 6 8 10];
scatter(x, y, 'filled')

A A scatter plot with 5 blue filled circles at points (1,2), (2,4), (3,6), (4,8), (5,10)

B A scatter plot with 5 red filled circles at points (1,2), (2,4), (3,6), (4,8), (5,10)

C A line plot connecting points (1,2), (2,4), (3,6), (4,8), (5,10)

D Syntax error due to missing marker size argument

💡 Hint

The 'filled' option fills the markers with the default color.

The scatter function plots points as circles by default. The 'filled' option fills these circles with the default blue color. No line is drawn connecting points.

❓ Predict Output

intermediate

Effect of Marker Size in Scatter Plot

What is the effect of the marker size argument in this MATLAB scatter plot code?

MATLAB

x = 1:3;
y = [3 6 9];
scatter(x, y, 100, 'r')

A Syntax error because marker size must be a vector

B Plots 3 red circles with default marker size at points (1,3), (2,6), (3,9)

C Plots 3 red circles with marker size 100 (large markers) at points (1,3), (2,6), (3,9)

D Plots 3 blue circles with marker size 100 at points (1,3), (2,6), (3,9)

💡 Hint

The third argument in scatter is the marker size in points squared.

The number 100 sets the marker size to be large. The color 'r' sets the marker color to red.

🔧 Debug

advanced

Identify the Error in Scatter Plot Code

What error will this MATLAB code produce when run?

MATLAB

x = 1:4;
y = [2 4 6];
scatter(x, y)

A Error: Vectors x and y must be the same length

B No error, plots 3 points ignoring extra x value

C Error: Missing marker size argument

D Plots 4 points with y values repeated

💡 Hint

Check the length of x and y vectors.

The scatter function requires x and y to have the same number of elements. Here x has 4 elements but y has 3, causing an error.

🧠 Conceptual

advanced

Understanding Color Mapping in Scatter Plots

Given the code below, what does the vector 'c' control in the scatter plot?

MATLAB

x = 1:5;
y = [5 4 3 2 1];
c = [10 20 30 40 50];
scatter(x, y, 100, c, 'filled')
colorbar

A 'c' is ignored because color is set by 'filled'

B 'c' controls the size of each marker

C 'c' sets the transparency of each marker

D 'c' controls the color of each marker based on its value, mapped to a colormap

💡 Hint

The fourth argument in scatter can be a vector for color data.

The vector 'c' assigns a color value to each point. The colorbar shows the mapping from values to colors.

🚀 Application

expert

Creating a Scatter Plot with Variable Marker Sizes and Colors

Which code snippet correctly creates a scatter plot with x and y coordinates, marker sizes proportional to y values, and colors mapped to x values?

A x = 1:4; y = [10 20 30 40]; scatter(x, y, x, y, 'filled')

B x = 1:4; y = [10 20 30 40]; scatter(x, y, y, x, 'filled')

C x = 1:4; y = [10 20 30 40]; scatter(x, y, y, 'filled', x)

D x = 1:4; y = [10 20 30 40]; scatter(x, y, 'filled', y, x)

💡 Hint

The third argument is marker size, the fourth is color data.

The scatter function syntax is scatter(x, y, size, color, 'filled'). Option B correctly assigns marker sizes to y and colors to x.