plot() function basics in MATLAB - Step-by-Step Execution

Concept Flow - plot() function basics

Define x and y data

↓

Call plot(x, y)

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MATLAB creates a figure window

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Draw line connecting points (x(i), y(i))

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Display plot on screen

The plot() function takes x and y data, creates a figure, draws lines connecting points, and shows the plot.

Execution Sample

MATLAB

x = 1:4;
y = [10 20 15 25];
plot(x, y);

This code plots points (1,10), (2,20), (3,15), (4,25) connected by lines.

Execution Table

Step	Action	x	y	Plot State	Output
1	Define x	[1 2 3 4]	-	No plot yet	No output
2	Define y	-	[10 20 15 25]	No plot yet	No output
3	Call plot(x,y)	[1 2 3 4]	[10 20 15 25]	Figure created, line drawn connecting points	Plot window opens showing line graph
4	Display plot	-	-	Plot visible with points connected by lines	Graph shown on screen

💡 Plot displayed; no further code to execute

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
x	undefined	[1 2 3 4]	[1 2 3 4]	[1 2 3 4]	[1 2 3 4]
y	undefined	undefined	[10 20 15 25]	[10 20 15 25]	[10 20 15 25]

Key Moments - 3 Insights

Why does the plot() function need both x and y vectors?

Because plot() connects points using pairs (x(i), y(i)). Without both, it cannot know where to place points. See execution_table step 3 where plot(x,y) uses both vectors.

What happens if x and y have different lengths?

MATLAB will give an error because it cannot pair points properly. In the execution_table, x and y have the same length, so plot works.

Does plot() show the graph immediately after calling it?

Yes, plot() creates the figure and draws the line immediately, as shown in execution_table step 3 and 4.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the value of y?

A undefined

B [10 20 15 25]

C [1 2 3 4]

D empty

💡 Hint

Check the 'y' column at step 2 in execution_table; it is defined after step 2.

At which step does the plot window open?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Output' column in execution_table; plot window opens at step 3.

If x was [1 2 3] but y was [10 20 15 25], what would happen?

A Plot shows all 4 points ignoring x

B Plot shows only first 3 points

C MATLAB throws an error

D Plot shows no points

💡 Hint

Recall key_moments about vector length mismatch causing errors.

Concept Snapshot

plot(x, y) draws a line graph connecting points (x(i), y(i))
x and y must be vectors of the same length
MATLAB opens a figure window to display the plot
Use plot() to visualize data points simply

Full Transcript

The plot() function in MATLAB draws a line graph from x and y data vectors. First, you define x and y arrays of the same length. Then calling plot(x, y) creates a figure window and draws lines connecting each point pair. The execution table shows step-by-step how variables x and y are defined, then plot() is called, and finally the graph appears. Key moments include understanding why x and y must match in length and that plot() immediately displays the graph. The visual quiz tests understanding of variable values and plot behavior at each step.