Signal routing in MATLAB - Step-by-Step Execution

Concept Flow - Signal routing

Input Signal

↓

Routing Decision

↓

Route 1

↓

Process 1

↓

Output Signal

The input signal is checked and routed based on a condition to one of two processing paths, then combined into the output.

Execution Sample

MATLAB

inputSignal = 5;
if inputSignal > 3
    routedSignal = inputSignal * 2;
else
    routedSignal = inputSignal + 1;
end
outputSignal = routedSignal;

This code routes the input signal to two different operations based on its value and produces an output.

Execution Table

Step	inputSignal	Condition (inputSignal > 3)	Branch Taken	routedSignal	outputSignal
1	5	5 > 3 is True	Yes (if branch)	5 * 2 = 10
2					10
Exit		Condition checked once	Routing done	Value assigned	Output assigned

💡 Routing decision made once; outputSignal assigned from routedSignal.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
inputSignal	undefined	5	5	5
routedSignal	undefined	10	10	10
outputSignal	undefined	undefined	10	10

Key Moments - 2 Insights

Why does routedSignal get the value 10 instead of 6?

Because inputSignal is 5, which is greater than 3, so the 'if' branch multiplies it by 2 (5*2=10) as shown in execution_table step 1.

What happens if inputSignal is 2?

The condition inputSignal > 3 would be false, so the 'else' branch runs, adding 1 to inputSignal (2+1=3). This would change routedSignal to 3.

Visual Quiz - 3 Questions

Look at the execution table, what is routedSignal after step 1?

A 10

B 5

C 6

D Undefined

💡 Hint

Check the 'routedSignal' column in execution_table at step 1.

At which step is outputSignal assigned a value?

A Step 1

B Step 2

C Exit

D Before Step 1

💡 Hint

Look at the 'outputSignal' column in execution_table; it gets a value at step 2.

If inputSignal was 1, what would routedSignal be?

A 2

B 1

C 3

D 0

💡 Hint

Refer to key_moments explanation about inputSignal less than or equal to 3.

Concept Snapshot

Signal routing uses conditions to send input signals down different paths.
Syntax: if condition, route one way; else, route another.
Output depends on which branch runs.
Useful for processing signals differently based on value.

Full Transcript

This example shows signal routing in MATLAB using an if-else condition. The inputSignal is checked if it is greater than 3. If true, routedSignal is inputSignal multiplied by 2. Otherwise, routedSignal is inputSignal plus 1. Finally, outputSignal is assigned the routedSignal value. The execution table traces these steps, showing variable values and branches taken. Key moments clarify why routedSignal becomes 10 when inputSignal is 5 and what happens if inputSignal is less than or equal to 3. The visual quiz tests understanding of variable values at each step and the routing logic. This teaches how to route signals conditionally in code.

Practice

1. What is the main purpose of signal routing in MATLAB programming?

easy

A. To send data to different parts of a program based on conditions

B. To create graphical user interfaces

C. To perform mathematical calculations only

D. To store data permanently on disk

Solution

1. Step 1: Understand signal routing concept

   Signal routing means directing data flow to different parts depending on conditions.

2. Step 2: Match purpose with options

   Only To send data to different parts of a program based on conditions describes sending data based on conditions, which is signal routing.

3. Final Answer:

   To send data to different parts of a program based on conditions -> Option A

4. Quick Check:

   Signal routing = conditional data flow [OK]

Hint: Signal routing controls data flow based on conditions [OK]

Common Mistakes:

• Confusing signal routing with data storage
• Thinking it only does calculations
• Mixing it up with GUI creation

2. Which of the following is the correct syntax to route a signal based on a condition in MATLAB?

easy

A. if signal > 0 {
output = signal;
} else {
output = 0;
}

B. if (signal > 0) then
output = signal
else
output = 0
end if

C. if signal > 0
output = signal;
else
output = 0;
end

D. if signal > 0:
output = signal
else:
output = 0

Solution

1. Step 1: Recall MATLAB if-else syntax

   MATLAB uses 'if condition', statements, 'else', statements, and 'end' to close.

2. Step 2: Compare options with MATLAB syntax

   if signal > 0 output = signal; else output = 0; end matches MATLAB syntax exactly; others use syntax from other languages.

3. Final Answer:

   if signal > 0 output = signal; else output = 0; end -> Option C

4. Quick Check:

   MATLAB if-else ends with 'end' [OK]

Hint: MATLAB if-else blocks end with 'end' keyword [OK]

Common Mistakes:

• Using 'then' keyword (not in MATLAB)
• Using braces {} instead of end
• Using colons like Python

3. What will be the output of this MATLAB code?

signal = -5;
if signal > 0
    routed = 1;
else
    routed = -1;
end
routed

medium

A. -1

B. 1

C. 0

D. Error

Solution

1. Step 1: Check the condition signal > 0

   signal is -5, which is not greater than 0, so condition is false.

2. Step 2: Follow else branch

   Since condition is false, routed is assigned -1.

3. Final Answer:

   -1 -> Option A

4. Quick Check:

   signal = -5 -> routed = -1 [OK]

Hint: Check condition truth to pick if or else branch [OK]

Common Mistakes:

• Assuming negative numbers satisfy > 0
• Confusing output variable name
• Expecting zero output

4. Identify the error in this MATLAB signal routing code:

signal = 10;
if signal > 5
    output = 1;
else
    output = 0;

medium

A. Variable 'output' is not defined

B. Missing 'end' to close the if statement

C. Incorrect comparison operator

D. Using semicolons incorrectly

Solution

1. Step 1: Check if statement structure

   MATLAB requires 'end' to close if blocks.

2. Step 2: Verify code completeness

   The code lacks 'end' after else block, causing syntax error.

3. Final Answer:

   Missing 'end' to close the if statement -> Option B

4. Quick Check:

   if blocks must end with 'end' [OK]

Hint: Always close if with 'end' in MATLAB [OK]

Common Mistakes:

• Forgetting 'end' after if-else
• Thinking semicolons end blocks
• Misusing comparison operators

5. You want to route a signal in MATLAB to three different outputs based on its value:
- If signal < 0, output = -1
- If signal == 0, output = 0
- If signal > 0, output = 1
Which code correctly implements this routing?

hard

A. if signal < 0
output = -1;
else if signal == 0
output = 0;
else
output = 1;
end

B. if signal <= 0
output = -1;
elseif signal == 0
output = 0;
else
output = 1;
end

C. if signal < 0
output = -1;
if signal == 0
output = 0;
else
output = 1;
end

D. if signal < 0
output = -1;
elseif signal == 0
output = 0;
else
output = 1;
end

Solution

1. Step 1: Understand routing conditions

   We need three cases: less than 0, equal to 0, greater than 0.

2. Step 2: Check code correctness

   if signal < 0 output = -1; elseif signal == 0 output = 0; else output = 1; end uses if, elseif, else correctly with proper conditions and 'end'.

3. Step 3: Identify errors in other options

   if signal <= 0 output = -1; elseif signal == 0 output = 0; else output = 1; end wrongly uses <= which overlaps conditions; C uses two separate ifs causing logic errors; D uses 'else if' which is invalid syntax in MATLAB.

4. Final Answer:

   if signal < 0 output = -1; elseif signal == 0 output = 0; else output = 1; end -> Option D

5. Quick Check:

   Use if-elseif-else for multiple conditions [OK]

Hint: Use if-elseif-else for multiple exclusive conditions [OK]

Common Mistakes:

• Using overlapping conditions like <= and ==
• Using nested if without else properly
• Writing 'else if' instead of 'elseif'