plot() function basics in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this plot command?

Consider the following MATLAB code snippet:

x = 1:5;
y = x.^2;
plot(x, y)

What does this plot show?

MATLAB

x = 1:5;
y = x.^2;
plot(x, y)

A A line graph with points (1,1), (2,4), (3,9), (4,16), (5,25) connected by straight lines

B A scatter plot with points (1,1), (2,4), (3,9), (4,16), (5,25) but no lines connecting them

C A bar chart with bars at x=1 to 5 with heights 1,4,9,16,25

D A pie chart showing the values 1,4,9,16,25 as slices

💡 Hint

The plot() function connects points with lines by default.

The plot(x, y) command in MATLAB creates a line plot connecting the points defined by vectors x and y. Here, y = x squared, so the points are (1,1), (2,4), (3,9), (4,16), (5,25).

❓ Predict Output

intermediate

What color and marker style does this plot use?

Look at this MATLAB code:

x = 0:0.5:2;
y = sin(pi*x);
plot(x, y, 'ro--')

What does the plot look like?

MATLAB

x = 0:0.5:2;
y = sin(pi*x);
plot(x, y, 'ro--')

A Black stars connected by dash-dot lines

B Blue squares connected by solid lines

C Green triangles connected by dotted lines

D Red circles connected by dashed lines

💡 Hint

The format string 'ro--' means red color, circle marker, dashed line.

In MATLAB plot format strings, 'r' means red color, 'o' means circle marker, and '--' means dashed line. So the plot shows red circles connected by dashed lines.

🔧 Debug

advanced

Why does this plot command cause an error?

Examine this MATLAB code:

x = 1:5;
y = [2, 4, 6];
plot(x, y)

What error occurs and why?

MATLAB

x = 1:5;
y = [2, 4, 6];
plot(x, y)

A No error, plot shows points with missing values

B Error because y contains even numbers only

C Error because x and y vectors have different lengths

D Error because x is not a column vector

💡 Hint

Check if x and y have the same number of elements.

The plot function requires x and y to have the same length. Here, x has 5 elements but y has only 3, so MATLAB throws an error about dimension mismatch.

🧠 Conceptual

advanced

What happens if you call plot with a single vector?

In MATLAB, what does the command plot([3 1 4 1 5]) do?

MATLAB

plot([3 1 4 1 5])

A Plots the vector values on the y-axis against their indices on the x-axis

B Plots the vector values on the x-axis against their indices on the y-axis

C Raises an error because two arguments are required

D Plots a horizontal line at y=3

💡 Hint

When only one vector is given, MATLAB uses indices as x values.

If plot is called with one vector, MATLAB plots the vector values on the y-axis and uses the indices (1,2,3,...) as x-axis values.

❓ Predict Output

expert

What is the output of this multi-line plot command?

Consider this MATLAB code:

x = 0:pi/4:pi;
y1 = sin(x);
y2 = cos(x);
plot(x, y1, '-b', x, y2, ':r')

What does the plot show?

MATLAB

x = 0:pi/4:pi;
y1 = sin(x);
y2 = cos(x);
plot(x, y1, '-b', x, y2, ':r')

A Only sin(x) plotted with a blue dashed line

B A blue solid line for sin(x) and a red dotted line for cos(x)

C A red solid line for sin(x) and a blue dotted line for cos(x)

D Only cos(x) plotted with a red solid line

💡 Hint

The format '-b' means blue solid line, ':r' means red dotted line.

The plot command plots two lines: sin(x) with a blue solid line and cos(x) with a red dotted line, using the specified format strings.