switch statement in R


Switch case statements are a substitute for long if statements that compare a variable to several integral values. Switch case in R is a multiway branch statement. It allows a variable to be tested for equality against a list of values.

Switch statement follows the approach of mapping and searching over a list of values. If there is more than one match for a specific value, then the switch statement will return the first match found of the value matched with the expression.

Syntax:
switch(expression, case1, case2, case3....)

Here, the expression is matched with the list of values and the corresponding value is returned.

Important Points about Switch Case Statements:
An expression type with character string always matched to the listed cases.
An expression which is not a character string then this exp is coerced to integer.
For multiple matches, the first match element will be used.
No default argument case is available there in R switch case.
An unnamed case can be used, if there is no matched case.
Example-1
x <- switch(  
3,  
"Susmitha",  
"Nibu",  
"Binu",     
"Sumit"  
)  
print(x)  
output:
[1] "Binu"

Example-2
ax= 1  
bx = 2  
y = switch(  
    ax+bx,  
    "Hello, Padma",  
    "Hello Arpita",  
    "Hello Binu",  
    "Hello Nishka"  
)  
print (y)  
output:
[1] "Hello Binu"

y = "18"  
x = switch(  
    y,  
    "9"="Hello Arpita",  
    "12"="Hello Vaishali",  
    "18"="Hello Nishka",  
    "21"="Hello Shubham"  
)  
   
print (x)  

output:
[1]"Hello Nishka"

In case of multiple matches, the value of first matching element is returned.
# Select first match and return its value 
x <- "a" 
v <- switch(x, "a"="apple", "a"="apricot", "a"="avocado") 
print(v)

output:
 [1] "apple"

Default case

In the case of no match, the unnamed element (if any) is returned. If there are more than one unnamed elements present, an error is raised.

# Select unnamed element in the case of no match
x <- "z"
v <- switch(x, "a"="apple", "b"="banana", "c"="cherry", "grapes")
print(v)

output:
[1]"grapes"


If the numeric value is out of range (greater than the number of choices), NULL is returned.
x <- 5 
v <- switch(x, "apple", "banana", "cherry") 
print(v)

output:
NULL



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