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



Comments

Post a Comment

Popular posts from this blog

Programming in R - Dr Binu V P

About me Introduction R Data Types R Variables Syntax /Elements of R program comments/keywords R Input/Output R Operators Control Statements in R     if and if else statements      switch statement     for loop- break and next statement     while loop     repeat loop Functions           Functions in R          Recursive Functions in R   Data Structures            Data Structures in R          Strings         Vectors         Lists          Matrices and Arrays         Data Frames         Factors  R Graphs and Charts         R Plots          R Line Graphs         R Scatter Plots          R Bar Plots          R Pie Charts          R Histogram          R Box Plot          R Strip Charts         Saving Plots in R R Data Manipulation           R Data Sets           R Basic Statistics         Data Handling in R         Read and write CSV files in R          Read and write xlsx files in R R Statistics          Central Tendency- Mean Median Mode         Measures of Variability- Range Variance an
Read more

Introduction

R is a free and open-source scripting language developed by Ross Ihaka and Robert Gentleman also known as “R & R” of the Statistics Department of the University of Auckland.in 1993. It's an alternative implementation of the S programming language, which was widely used in the 1980s for statistical computing. The R environment is designed to perforrm complex statistical analysis and display results using many visual graphics. The R progamming languague is written in C, Fortran, and R itself. Most R packages are written in the R programming language, but heavy computational chucks are written in C, C++, and Fortran. R allows integration with Python, C, C++, .Net, and Fortran. R is a language and environment for statistical computing and graphics. It is a GNU project which is similar to the S language and environment which was developed at Bell Laboratories (formerly AT&T, now Lucent Technologies) by John Chambers and colleagues. R can be considered as a different implementa
Read more

R Data Types

Data types are used in computer programming to specify the kind of data that can be stored in a variable. For effective memory consumption and precise computation, the right data type must be selected. Each data type has its own set of regulations and restrictions. There are fundamentally five data types in R. Though straight forward and obvious at first glance, they have a few surprises hidden in them. These elementary data types are: Numeric Integer Complex Character Logical These data types are often combined to form data structures. Let us explore the meaning of each data type in detail. Numeric Datatype in R Decimal values are called numerics in R. It is the default R data type for numbers in R. If you assign a decimal value to a variable x as follows, x will be of numeric type. Real numbers with a decimal point are represented using this data type in R. it uses a format for double-precision floating-point numbers to represent numerical values. # A simple R program # to illustrat
Read more