plot3 for 3D lines in MATLAB - Step-by-Step Execution

Concept Flow - plot3 for 3D lines

Define X, Y, Z vectors

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Call plot3(X, Y, Z)

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MATLAB draws 3D line

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Display 3D plot window

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User can rotate and view line in 3D

First, you create three lists of points for X, Y, and Z. Then, plot3 connects these points in 3D space and shows the line in a window you can rotate.

Execution Sample

MATLAB

X = [1 2 3 4];
Y = [2 3 4 5];
Z = [3 4 5 6];
plot3(X, Y, Z);
grid on;

This code draws a 3D line connecting points (1,2,3), (2,3,4), (3,4,5), and (4,5,6) with a grid shown.

Execution Table

Step	Action	X	Y	Z	Result
1	Define X vector	[1 2 3 4]			X points set
2	Define Y vector		[2 3 4 5]		Y points set
3	Define Z vector			[3 4 5 6]	Z points set
4	Call plot3(X,Y,Z)	[1 2 3 4]	[2 3 4 5]	[3 4 5 6]	3D line plotted connecting points
5	Enable grid				Grid shown on plot
6	Display plot window				3D plot window appears with line

💡 All points plotted and 3D line displayed; execution ends.

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	[2 3 4 5]	[2 3 4 5]	[2 3 4 5]
Z	undefined	undefined	undefined	[3 4 5 6]	[3 4 5 6]

Key Moments - 3 Insights

Why do X, Y, and Z vectors need to be the same length?

Because plot3 connects points by matching elements at the same index in X, Y, and Z. If lengths differ, MATLAB gives an error or unexpected plot. See execution_table rows 1-3 where vectors are all length 4.

What happens if you forget to call plot3 and just define X, Y, Z?

No plot appears because defining vectors only stores data. The actual drawing happens at plot3 call (row 4). Without it, no line is drawn.

Why do we use grid on after plot3?

grid on adds a grid to the 3D plot for easier viewing. It does not affect the line but helps see the 3D space better (row 5).

Visual Quiz - 3 Questions

Look at the execution_table at step 4. What does plot3 do with X, Y, Z?

A Draws a 3D line connecting points from X, Y, Z

B Creates separate 2D plots for X, Y, and Z

C Only plots X and Y ignoring Z

D Clears the vectors X, Y, Z

💡 Hint

See execution_table row 4 'Result' column describing the 3D line plotted.

At which step do the variables X, Y, and Z get their final values?

A Step 4

B Step 2

C Step 3

D Step 1

💡 Hint

Check variable_tracker columns 'After Step 3' where all vectors are defined.

If you change X to have 5 elements but Y and Z have 4, what happens?

A MATLAB plots only first 4 points

B MATLAB throws an error about vector length mismatch

C MATLAB ignores X and plots Y and Z

D MATLAB plots all 5 points ignoring Y and Z

💡 Hint

Recall key_moments about vector length needing to match for plot3.

Concept Snapshot

plot3(X,Y,Z) draws a 3D line connecting points defined by vectors X, Y, and Z.
Vectors must be the same length.
Call grid on to add a grid for better 3D view.
The plot window allows rotation to see the line from different angles.
Use plot3 for simple 3D line visualization.

Full Transcript

This visual execution shows how MATLAB's plot3 function works for drawing 3D lines. First, you define three vectors X, Y, and Z with the same number of points. Then, calling plot3(X,Y,Z) connects these points in 3D space with a line. Adding grid on shows a grid to help see the 3D plot better. The execution table traces each step: defining vectors, calling plot3, enabling grid, and displaying the plot window. The variable tracker shows how X, Y, and Z get their values step by step. Key moments clarify why vectors must be equal length, why plot3 is needed to draw, and the purpose of grid on. The quiz tests understanding of plot3's behavior and vector requirements. This helps beginners see exactly how 3D lines are created and displayed in MATLAB.