Line styles, markers, and colors in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this MATLAB plot command?

Consider the following MATLAB code snippet:

plot(1:5, 'r--o')

What does this command produce in terms of line style, marker, and color?

MATLAB

plot(1:5, 'r--o')

A A red solid line with square markers

B A blue solid line with circle markers

C A red dashed line with circle markers

D A green dotted line with star markers

💡 Hint

The string 'r--o' specifies color, line style, and marker in that order.

In MATLAB plot syntax, 'r' means red color, '--' means dashed line, and 'o' means circle markers. So the plot shows a red dashed line with circle markers.

❓ Predict Output

intermediate

What color and marker does this plot use?

Given the MATLAB command:

plot(1:3, 'g:*')

What is the color, line style, and marker used?

MATLAB

plot(1:3, 'g:*')

A Green solid line with circle markers

B Green dotted line with star markers

C Blue dotted line with star markers

D Red dashed line with square markers

💡 Hint

The order is color, line style, then marker.

'g' means green color, ':' means dotted line, and '*' means star markers.

❓ Predict Output

advanced

What is the output of this MATLAB plot command with multiple style characters?

Analyze the MATLAB command:

plot(1:4, 'b-.s')

What line style, marker, and color does this produce?

MATLAB

plot(1:4, 'b-.s')

A Blue dash-dot line with square markers

B Blue dashed line with circle markers

C Black dash-dot line with square markers

D Blue solid line with star markers

💡 Hint

Remember 'b' is blue, '-.' is dash-dot line, and 's' is square marker.

The color 'b' is blue, '-.' is dash-dot line style, and 's' is square marker.

❓ Predict Output

advanced

What error or output does this MATLAB plot command produce?

Consider this MATLAB command:

plot(1:5, 'r-o-')

What happens when you run this?

MATLAB

plot(1:5, 'r-o-')

A Plots a red dotted line with square markers

B Plots a red solid line with circle markers

C Plots a red dashed line with circle markers

D Syntax error due to invalid line style string

💡 Hint

Line style strings must be in a valid order and format.

The string 'r-o-' is invalid because it repeats line style characters incorrectly, causing a syntax error.

🧠 Conceptual

expert

How many unique line style and marker combinations are possible with MATLAB's basic plot specifiers?

MATLAB basic plot specifiers include 7 colors (b,g,r,c,m,y,k), 7 line styles (-, --, :, -., none, ' ', ''), and 9 marker types (o, +, *, ., x, s, d, ^, v).

How many unique combinations of color, line style, and marker can be created if you must specify exactly one color, one line style, and one marker?

A 315

B 63

C 441

D 49

💡 Hint

Multiply the number of options for each category.

7 colors × 7 line styles × 9 markers = 441 combinations. However, some line styles like 'none' or empty strings do not produce visible lines, so if excluding those, the count reduces. Assuming all line styles count, answer is 441. But if 'none' and empty strings are excluded (2 styles), then 5 line styles remain: 7×5×9=315.

Practice

1. Which of the following is the correct way to plot a red dashed line with circle markers in MATLAB?

easy

A. plot(x, y, 'ro-')

B. plot(x, y, '-ro')

C. plot(x, y, 'o-r')

D. plot(x, y, 'r--o')

Solution

1. Step 1: Understand MATLAB line style syntax

   In MATLAB, the format 'color lineStyle marker' is used inside the plot command, for example 'r--o' means red color, dashed line, and circle markers.

2. Step 2: Match the correct order

   The correct order is color first ('r'), then line style ('--'), then marker ('o'). So 'r--o' is correct.

3. Final Answer:

   plot(x, y, 'r--o') -> Option D

4. Quick Check:

   Color + line style + marker = 'r--o' [OK]

Hint: Remember order: color, line style, then marker [OK]

Common Mistakes:

• Putting marker before line style
• Using wrong order of characters
• Confusing color codes with markers

2. Which of the following MATLAB plot commands will produce a blue solid line with square markers?

easy

A. plot(x, y, 'b-s')

B. plot(x, y, 'sb:')

C. plot(x, y, 'b:sq')

D. plot(x, y, 'bs:')

Solution

1. Step 1: Identify the correct syntax for blue solid line with square markers

   In MATLAB, 'b' means blue, '-' means solid line, and 's' means square marker. The order is color, line style, marker.

2. Step 2: Check each option

   plot(x, y, 'b-s') 'b-s' correctly follows the order: blue color, solid line, square marker.

3. Final Answer:

   plot(x, y, 'b-s') -> Option A

4. Quick Check:

   Color + line style + marker = 'b-s' [OK]

Hint: Use 'color-lineStyle-marker' order in plot string [OK]

Common Mistakes:

• Mixing order of marker and line style
• Using invalid marker codes
• Adding extra characters like 'sq'

3. What will be the color and style of the line plotted by this command?

plot(x, y, 'g:*')

medium

A. Green dotted line with star markers

B. Green solid line with star markers

C. Green dash-dot line with star markers

D. Green dashed line with star markers

Solution

1. Step 1: Decode the plot style string 'g:*'

   'g' means green color, ':' means dotted line style, and '*' means star markers.

2. Step 2: Combine the meanings

   The line will be green, dotted, with star markers.

3. Final Answer:

   Green dotted line with star markers -> Option A

4. Quick Check:

   Color = green, line style = dotted, marker = star [OK]

Hint: ':' means dotted line, '*' means star marker [OK]

Common Mistakes:

• Confusing ':' with dash-dot line
• Mixing marker and line style symbols
• Assuming solid line by default

4. Identify the error in this MATLAB plot command:

plot(x, y, 'r--x-o')

medium

A. Color code 'r' is incorrect

B. Multiple markers specified, which is invalid

C. Line style '--' cannot be combined with markers

D. Missing semicolon at the end

Solution

1. Step 1: Analyze the plot style string 'r--x-o'

   This string tries to specify two markers: 'x' and 'o', which is not allowed in MATLAB plot format.

2. Step 2: Understand MATLAB plot style rules

   Only one marker can be specified along with one line style and one color. Multiple markers are invalid.

3. Final Answer:

   Multiple markers specified, which is invalid -> Option B

4. Quick Check:

   Only one marker allowed in plot style [OK]

Hint: Use only one marker symbol in plot style string [OK]

Common Mistakes:

• Adding multiple markers in one style string
• Ignoring MATLAB plot style syntax rules
• Thinking semicolon affects plot style

5. You want to plot two lines on the same graph: one with a green dash-dot line and circle markers, and the other with a magenta dotted line and square markers. Which MATLAB code correctly does this?

hard

A. plot(x1, y1, 'g-.o'); plot(x2, y2, 'm:s');

B. plot(x1, y1, 'g-o.'); hold on; plot(x2, y2, 'm.s:'); hold off;

C. plot(x1, y1, 'g-.o'); hold on; plot(x2, y2, 'm:s'); hold off;

D. plot(x1, y1, 'g:o-'); hold on; plot(x2, y2, 'm-s.'); hold off;

Solution

1. Step 1: Understand the required styles

   First line: green ('g'), dash-dot ('-.'), circle marker ('o'). Second line: magenta ('m'), dotted (':'), square marker ('s').

2. Step 2: Check each option for correct syntax and use of 'hold on'

   plot(x1, y1, 'g-.o'); hold on; plot(x2, y2, 'm:s'); hold off; uses 'g-.o' and 'm:s' correctly and uses 'hold on' to plot both lines on the same graph.

3. Step 3: Verify other options

   plot(x1, y1, 'g-o.'); hold on; plot(x2, y2, 'm.s:'); hold off; and D have incorrect order or invalid style strings. plot(x1, y1, 'g-.o'); plot(x2, y2, 'm:s'); misses 'hold on' so second plot overwrites first.

4. Final Answer:

   plot(x1, y1, 'g-.o'); hold on; plot(x2, y2, 'm:s'); hold off; -> Option C

5. Quick Check:

   Use correct style strings and 'hold on' to combine plots [OK]

Hint: Use 'hold on' to plot multiple lines with different styles [OK]

Common Mistakes:

• Forgetting 'hold on' to keep previous plots
• Mixing order of line style and marker
• Using invalid style strings like 'g:o-'