Switch statement in R Programming - Step-by-Step Execution

Concept Flow - Switch statement

Start

↓

Evaluate expression

↓

Match case?

No→Default case if exists

Yes↓

Execute matched case

↓

End

The switch statement evaluates an expression, matches it to a case, executes that case, or the default if no match.

Execution Sample

R Programming

x <- "b"
switch(x,
       a = "Apple",
       b = "Banana",
       c = "Cherry",
       "Unknown fruit")

This code uses switch to return a fruit name based on the value of x.

Execution Table

Step	Expression Value	Case Checked	Match?	Action	Output
1	"b"	a	No	Check next case
2	"b"	b	Yes	Return "Banana"	Banana
3	N/A	Stop	N/A	Exit switch	Banana

💡 Match found at case 'b', switch returns 'Banana' and stops.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
x	"b"	"b"	"b"	"b"

Key Moments - 2 Insights

What happens if the expression value does not match any case?

If no case matches, the switch returns the default value (last unnamed argument). See execution_table exit_note for no-match scenario.

Does switch check all cases even after a match?

No, switch stops checking after the first match, as shown in execution_table step 2 and 3.

Visual Quiz - 3 Questions

Look at the execution table, what is the output at step 2?

A "Cherry"

B "Banana"

C "Apple"

D "Unknown fruit"

💡 Hint

Check the 'Output' column at step 2 in the execution_table.

At which step does the switch stop checking cases?

A Step 3

B Step 1

C Step 2

D It checks all cases

💡 Hint

Look at the 'Action' column in steps 2 and 3 in execution_table.

If x was "d", what would the output be?

A "Cherry"

B "Banana"

C "Unknown fruit"

D "Apple"

💡 Hint

Refer to key_moments about default case when no match is found.

Concept Snapshot

switch(expression, case1 = value1, case2 = value2, ..., default)
- Evaluates expression once
- Matches expression to cases by name or position
- Executes first matching case
- Returns default if no match
- Stops after first match

Full Transcript

The switch statement in R evaluates an expression and compares it to each case in order. When it finds a matching case, it executes that case and stops checking further cases. If no case matches, it returns the default value, which is the last unnamed argument. For example, if x is "b", switch returns "Banana" because it matches the case named "b". If x does not match any case, switch returns the default value like "Unknown fruit". This behavior helps select one value from many options based on a single expression.