Multiple plots (hold on) in MATLAB - Step-by-Step Execution

Concept Flow - Multiple plots (hold on)

Start

↓

Plot first graph

↓

hold on activated

↓

Plot second graph

↓

Plot more graphs if needed

↓

hold off to stop adding

↓

End

The flow shows plotting the first graph, turning 'hold on' to keep the plot, adding more plots, then turning 'hold off' to finish.

Execution Sample

MATLAB

x = 0:0.1:2*pi;
y1 = sin(x);
y2 = cos(x);
plot(x,y1)
hold on
plot(x,y2)
hold off

This code plots sine and cosine on the same graph using 'hold on' to keep the first plot visible.

Execution Table

Step	Action	Plot State	Output
1	Create x, y1, y2 arrays	No plot yet	Variables ready
2	plot(x,y1)	Plot shows sine curve	Sine curve visible
3	hold on	Hold activated	Next plots added on same graph
4	plot(x,y2)	Sine and cosine curves visible	Cosine curve added
5	hold off	Hold deactivated	No more plots added automatically
6	End	Final plot with sine and cosine	Plot window shows both curves

💡 All plots added; hold off stops further additions.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	Final
x	undefined	[0 0.1 ... 6.28]	[0 0.1 ... 6.28]	[0 0.1 ... 6.28]	[0 0.1 ... 6.28]
y1	undefined	sin(x) values	sin(x) values	sin(x) values	sin(x) values
y2	undefined	cos(x) values	cos(x) values	cos(x) values	cos(x) values

Key Moments - 2 Insights

Why does the second plot replace the first if 'hold on' is not used?

Without 'hold on', each plot command clears the previous plot, so only the last plot shows. See step 2 and 4 in execution_table where hold on is activated to keep both.

What happens if 'hold off' is not called after plotting multiple graphs?

'hold off' stops adding new plots on the same figure. If omitted, new plots will continue to add until MATLAB session ends or figure is closed. See step 5 for hold off effect.

Visual Quiz - 3 Questions

Look at the execution_table, what is the plot state after step 3?

A Only sine curve is visible; hold is off

B Hold is activated; next plots add on same graph

C Plot window is cleared

D Cosine curve is visible alone

💡 Hint

Check the 'Plot State' column at step 3 in execution_table

At which step does the cosine curve first appear on the plot?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the 'Output' column in execution_table for when cosine curve is added

If 'hold off' was not called, what would happen when plotting a third graph?

A The third graph would replace the previous two

B An error would occur

C The third graph would be added on the same plot

D The plot window would close

💡 Hint

Refer to key_moments about hold off effect and execution_table step 5

Concept Snapshot

plot(x,y) draws a graph.
hold on keeps current plot.
plot more graphs to add on same figure.
hold off stops adding plots.
Use to compare multiple data sets visually.

Full Transcript

This example shows how to plot multiple graphs on the same figure in MATLAB. First, we create x values and two y arrays for sine and cosine. We plot the sine curve. Then, we use 'hold on' to keep this plot visible. Next, we plot the cosine curve, which appears on the same graph. Finally, 'hold off' stops further plots from adding automatically. Without 'hold on', each new plot replaces the previous one. This technique helps compare multiple data sets visually in one figure.