Scatter plots in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic scatter plot of x and y.

MATLAB

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

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

Ax

B1:5

C[1,2,3]

Dy

Attempts:

3 left

💡 Hint

Common Mistakes

Using x twice instead of y for the second argument.

Passing a range instead of the y vector.

The scatter function plots points using x and y coordinates. Here, y is the vertical data.

2fill in blank

medium

Complete the code to add red color to the scatter plot points.

MATLAB

x = 1:5;
y = [3, 6, 9, 12, 15];
scatter(x, y, 36, [1]);

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

A'yellow'

B'red'

C'green'

D'blue'

Attempts:

3 left

💡 Hint

Common Mistakes

Using color names without quotes.

Using an unsupported color string.

The fourth argument in scatter sets the color of the points. 'red' colors points red.

3fill in blank

hard

Fix the error in the code to plot a scatter with circle markers.

MATLAB

x = 1:4;
y = [5, 10, 15, 20];
scatter(x, y, 100, 'b', [1]);

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

A'o'

B'*'

C's'

D'x'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' which is star marker, not circle.

Omitting quotes around the marker.

The marker type 'o' specifies circle markers in scatter plots.

4fill in blank

hard

Fill both blanks to create a scatter plot with blue square markers and size 50.

MATLAB

x = 1:3;
y = [7, 14, 21];
scatter(x, y, [1], [2], 's');

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

A50

B'red'

C'blue'

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping size and color arguments.

Using wrong marker type.

The third argument sets marker size (50), the fourth sets color ('blue'), and 's' sets square markers.

5fill in blank

hard

Fill all three blanks to create a scatter plot with green diamond markers, size 75, and label the x-axis as 'Time'.

MATLAB

x = 1:4;
y = [10, 20, 30, 40];
scatter(x, y, [1], [2], '[3]');
xlabel('Time');

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

A75

B'green'

C'd'

D'o'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong marker character.

Forgetting quotes around color or marker.

Size is 75, color is 'green', and 'd' sets diamond markers. xlabel labels the x-axis.

Practice

1. What does a scatter plot in MATLAB primarily show?

easy

A. A bar chart of grouped data

B. A continuous line connecting data points

C. Points representing pairs of values on an X-Y graph

D. A pie chart of category percentages

Solution

1. Step 1: Understand scatter plot purpose

   A scatter plot shows individual points for pairs of values, usually X and Y coordinates.

2. Step 2: Compare options to definition

   Only Points representing pairs of values on an X-Y graph describes points on an X-Y graph, which matches scatter plot behavior.

3. Final Answer:

   Points representing pairs of values on an X-Y graph -> Option C

4. Quick Check:

   Scatter plot = points on X-Y graph [OK]

Hint: Scatter plots show points, not lines or bars [OK]

Common Mistakes:

• Confusing scatter plot with line plot
• Thinking scatter plots show bars or pie slices
• Assuming scatter plots connect points

2. Which of the following is the correct MATLAB syntax to create a scatter plot of vectors x and y?

easy

A. plot.scatter(x, y)

B. scatter(x, y)

C. scatterplot(x, y)

D. scatter x, y

Solution

1. Step 1: Recall MATLAB scatter syntax

   The correct function to create scatter plots is scatter(x, y).

2. Step 2: Check other options for syntax errors

   Options A, C, and D are not valid MATLAB commands for scatter plots.

3. Final Answer:

   scatter(x, y) -> Option B

4. Quick Check:

   scatter function syntax = scatter(x, y) [OK]

Hint: Use scatter() function with parentheses and commas [OK]

Common Mistakes:

• Using dot notation like plot.scatter
• Typing scatterplot instead of scatter
• Omitting parentheses or commas

3. What will the following MATLAB code display?

x = 1:5;
y = [2 4 6 8 10];
scatter(x, y, 100, 'r', 'filled')

medium

A. A scatter plot with red filled circles sized 100 at points (1,2), (2,4), ..., (5,10)

B. A line plot connecting points from (1,2) to (5,10)

C. An error because 'filled' is not a valid option

D. A scatter plot with default size and blue color points

Solution

1. Step 1: Understand scatter parameters

   The code uses scatter(x, y, 100, 'r', 'filled') which sets point size to 100, color red ('r'), and fills the markers.

2. Step 2: Interpret the plot output

   The plot shows red filled circles at points (1,2), (2,4), (3,6), (4,8), and (5,10).

3. Final Answer:

   A scatter plot with red filled circles sized 100 at points (1,2), (2,4), ..., (5,10) -> Option A

4. Quick Check:

   scatter(x,y,100,'r','filled') = red filled circles [OK]

Hint: Size, color, and fill control marker appearance [OK]

Common Mistakes:

• Thinking 'filled' causes error
• Confusing scatter with line plot
• Ignoring size and color parameters

4. Identify the error in this MATLAB code for a scatter plot:

x = 1:4;
y = [5 6 7];
scatter(x, y)

medium

A. Vectors x and y have different lengths causing an error

B. scatter requires a third argument for size

C. scatter cannot plot numeric vectors

D. No error; code runs fine

Solution

1. Step 1: Check vector lengths

   Vector x has length 4, but y has length 3, which is invalid for scatter.

2. Step 2: Understand scatter input requirements

   Scatter requires x and y to be the same length to plot pairs of points.

3. Final Answer:

   Vectors x and y have different lengths causing an error -> Option A

4. Quick Check:

   Length mismatch in x,y vectors = error [OK]

Hint: x and y must be same length for scatter [OK]

Common Mistakes:

• Assuming scatter auto-fixes length mismatch
• Thinking size argument is mandatory
• Believing scatter can't plot numeric data

5. You have two groups of data points:

x1 = [1 2 3]; y1 = [4 5 6];
x2 = [1 2 3]; y2 = [7 8 9];

How can you plot both groups on the same scatter plot with different colors using filled markers and add a legend?

hard

A. plot(x1, y1, 'b'); plot(x2, y2, 'r'); legend('Group 1', 'Group 2')

B. scatter(x1, y1, 'b', 'filled'); scatter(x2, y2, 'r', 'filled'); legend('Group 1', 'Group 2')

C. scatter(x1, y1, 'b'); hold on; scatter(x2, y2, 'r'); legend('Group 1', 'Group 2')

D. scatter(x1, y1, 'b', 'filled'); hold on; scatter(x2, y2, 'r', 'filled'); legend('Group 1', 'Group 2')

Solution

1. Step 1: Plot first group with filled blue markers

   Use scatter(x1, y1, 'b', 'filled') to plot blue filled points.

2. Step 2: Use hold on before plotting second group

   To overlay plots, hold on keeps the first plot visible before adding the second.

3. Step 3: Plot second group with filled red markers and add legend

   Plot second group with scatter(x2, y2, 'r', 'filled') and add legend for clarity.

4. Final Answer:

   scatter(x1, y1, 'b', 'filled'); hold on; scatter(x2, y2, 'r', 'filled'); legend('Group 1', 'Group 2') -> Option D

5. Quick Check:

   Use hold on to overlay scatter plots with legend [OK]

Hint: Use hold on to combine scatter plots with different colors [OK]

Common Mistakes:

• Forgetting hold on causes second plot to overwrite first
• Using plot instead of scatter for points
• Omitting legend or using incorrect syntax