Axis control and formatting in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What MATLAB command sets the limits of the x-axis?

The xlim command sets the limits of the x-axis. For example, xlim([0 10]) sets the x-axis to range from 0 to 10.

intermediate

How do you change the scale of an axis to logarithmic in MATLAB?

Use the set(gca, 'XScale', 'log') or set(gca, 'YScale', 'log') command to change the x-axis or y-axis scale to logarithmic.

beginner

What does the MATLAB command axis equal do?

The command axis equal adjusts the plot so that the units are the same length on both x and y axes, making circles look like circles, not ellipses.

beginner

How can you add grid lines to a MATLAB plot?

Use the command grid on to add grid lines to the current plot, which helps in reading values more easily.

intermediate

Explain how to customize tick marks on an axis in MATLAB.

You can customize tick marks using xticks and yticks. For example, xticks([0 2 4 6]) sets x-axis ticks at 0, 2, 4, and 6.

Which command sets the y-axis limits to range from 1 to 100 in MATLAB?

A set(gca, 'YLim', [0 1])

B xlim([1 100])

C axis([1 100])

D ylim([1 100])

The ylim command sets the limits of the y-axis. ylim([1 100]) sets it from 1 to 100.

What does axis tight do in a MATLAB plot?

A Removes axis labels

B Makes axis scales logarithmic

C Sets axis limits to fit the data tightly

D Sets equal scaling on both axes

axis tight adjusts the axis limits to fit the data snugly without extra space.

How do you turn off grid lines in a MATLAB plot?

A grid off

B grid remove

C grid false

D no grid

The command grid off disables grid lines on the plot.

Which command changes the x-axis scale to logarithmic?

A xlog()

B set(gca, 'XScale', 'log')

C logscale x

D axis logx

Use set(gca, 'XScale', 'log') to set the x-axis to logarithmic scale.

What does axis equal ensure in a plot?

A Equal length units on x and y axes

B Equal number of ticks on both axes

C Equal axis limits

D Equal font size on axis labels

axis equal makes sure one unit on x is the same length as one unit on y.

Describe how to control axis limits and scales in MATLAB plots.

Think about commands that set limits and change linear to logarithmic scale.

Explain how to format a MATLAB plot to improve readability using axis control and grid lines.

Consider commands that adjust ticks, aspect ratio, and add grid lines.

Practice

1. What does the MATLAB command axis([0 10 0 5]) do to a plot?

easy

A. Sets the x-axis limits from 0 to 10 and y-axis limits from 0 to 5

B. Sets the axis color to RGB values [0 10 0 5]

C. Creates a grid with 10 rows and 5 columns

D. Labels the axes with numbers 0, 10, 0, and 5

Solution

1. Step 1: Understand the axis function input

   The axis function with a vector of four numbers sets axis limits: [xmin xmax ymin ymax].

2. Step 2: Apply the given limits

   Here, [0 10 0 5] means x-axis from 0 to 10 and y-axis from 0 to 5.

3. Final Answer:

   Sets the x-axis limits from 0 to 10 and y-axis limits from 0 to 5 -> Option A

4. Quick Check:

   axis([xmin xmax ymin ymax]) = set axis limits [OK]

Hint: Remember axis([xmin xmax ymin ymax]) sets axis limits [OK]

Common Mistakes:

• Confusing axis limits with colors
• Thinking axis sets labels or grid size
• Using axis without four numbers

2. Which of the following is the correct syntax to set the x-axis label to 'Time (s)' in MATLAB?

easy

A. labelx('Time (s)')

B. xlabel('Time (s)')

C. setxlabel('Time (s)')

D. xaxislabel('Time (s)')

Solution

1. Step 1: Recall MATLAB function for x-axis label

   The function to set x-axis label is xlabel with the label text as input.

2. Step 2: Check syntax correctness

   xlabel('Time (s)') correctly sets the label. Other options are invalid function names.

3. Final Answer:

   xlabel('Time (s)') -> Option B

4. Quick Check:

   Use xlabel('text') to label x-axis [OK]

Hint: Use xlabel('text') exactly to label x-axis [OK]

Common Mistakes:

• Using wrong function names like setxlabel
• Forgetting quotes around label text
• Confusing xlabel with axis or title

3. What will be the effect of the following MATLAB code?

plot(1:5, [2 4 6 8 10]);
axis([0 6 0 12]);
xticks([0 2 4 6]);
yticks([0 6 12]);

medium

A. Plot points with x-axis from 0 to 6, y-axis from 0 to 12, x-ticks at 0,2,4,6 and y-ticks at 0,6,12

B. Plot points with default axis limits and ticks

C. Error because xticks and yticks require vectors of length 5

D. Plot with reversed axes limits

Solution

1. Step 1: Analyze axis limits

   axis([0 6 0 12]) sets x-axis from 0 to 6 and y-axis from 0 to 12.

2. Step 2: Analyze tick settings

   xticks([0 2 4 6]) sets x-axis ticks at 0, 2, 4, 6; yticks([0 6 12]) sets y-axis ticks at 0, 6, 12.

3. Final Answer:

   Plot points with x-axis from 0 to 6, y-axis from 0 to 12, x-ticks at 0,2,4,6 and y-ticks at 0,6,12 -> Option A

4. Quick Check:

   axis + xticks + yticks control limits and ticks [OK]

Hint: axis sets limits; xticks/yticks set tick marks [OK]

Common Mistakes:

• Assuming default ticks remain after setting axis
• Thinking xticks/yticks need same length as data
• Confusing axis limits with tick positions

4. Identify the error in this MATLAB code snippet for setting axis limits and fix it:

plot(1:3, [5 10 15])
axis(0 3 0 20)

medium

A. Limits must be strings; use axis('0 3 0 20')

B. axis function does not set limits; use xlim and ylim instead

C. Missing square brackets around limits; should be axis([0 3 0 20])

D. No error; code runs fine

Solution

1. Step 1: Check axis function syntax

   The axis function requires a vector input for limits, enclosed in square brackets.

2. Step 2: Identify missing brackets

   The code uses axis(0 3 0 20) without brackets, causing syntax error.

3. Final Answer:

   Missing square brackets around limits; should be axis([0 3 0 20]) -> Option C

4. Quick Check:

   axis([xmin xmax ymin ymax]) needs brackets [OK]

Hint: Always use square brackets for axis limits [OK]

Common Mistakes:

• Omitting brackets around axis limits
• Using strings instead of numeric vectors
• Confusing axis with xlim or ylim functions

5. You want to create a plot with x-axis from -5 to 5, y-axis from -10 to 10, and custom ticks every 2 units on both axes. Which MATLAB code correctly achieves this?

hard

A. plot(x,y); axis([-5 5 -10 10]); xticks([-5 2 5]); yticks([-10 2 10]);

B. plot(x,y); axis([-5 5 -10 10]); xticks(-5:5); yticks(-10:10);

C. plot(x,y); xlim([-5 5]); ylim([-10 10]); ticks([-5 5], [-10 10]);

D. plot(x,y); axis([-5 5 -10 10]); xticks(-5:2:5); yticks(-10:2:10);

Solution

1. Step 1: Set axis limits correctly

   axis([-5 5 -10 10]) sets x-axis and y-axis limits as required.

2. Step 2: Set ticks every 2 units

   xticks(-5:2:5) creates ticks at -5, -3, -1, 1, 3, 5; similarly for y-axis with yticks(-10:2:10).

3. Step 3: Check other options

   plot(x,y); axis([-5 5 -10 10]); xticks([-5 2 5]); yticks([-10 2 10]); sets ticks incorrectly (missing intermediate values). plot(x,y); xlim([-5 5]); ylim([-10 10]); ticks([-5 5], [-10 10]); uses invalid ticks function. plot(x,y); axis([-5 5 -10 10]); xticks(-5:5); yticks(-10:10); sets ticks every 5 units, not 2.

4. Final Answer:

   plot(x,y); axis([-5 5 -10 10]); xticks(-5:2:5); yticks(-10:2:10); -> Option D

5. Quick Check:

   Use axis for limits and colon operator for ticks [OK]

Hint: Use colon operator for ticks: start:step:end [OK]

Common Mistakes:

• Setting ticks with wrong intervals
• Using non-existent ticks() function
• Confusing axis limits with tick values