## switch Statement

A switch statement in R allows a variable to be tested for equality against a list of values. Each value in a list is called a case, and the variable being switched on is checked for each case. R switch is almost the same as the if statement regarding working functionality. The basic syntax is

switch(expression, case 1, case 2, case 3, . . )

The expression values are tested against multiple cases (*case1, case2, …, casen*). The one-line syntax is,

An R Switch statement allows a default statement can also be added. The default statement will be executed, when the Expression value is not matching with any of the case statements. The following example is a simple command-line type calculator using R.

number1 <- 30 number2 <- 20 operator <- readline(prompt = "Enter any ARITHMETIC OPERATOR (+, -, *, ^, /, %/%, %%)!: ") switch(operator, "+" = print(paste("Addition (number1+number2) = ", number1 + number2)), "-" = print(paste("Subtraction (number1-number2) = ", number1 - number2)), "*" = print(paste("Multiplication (number1*number2) = ", number1 * number2)), "^" = print(paste("Exponent (number1^number2) = ", number1 ^ number2)), "/" = print(paste("Division (number1/number2) = ", number1 / number2)), "%/%" = print(paste("Integer Division (number1 %/% number2) = ", number1 %/% number2)), "%%" = print(paste("Division (number1 %% number2) = ", number1 %% number2)) )

From the above example, one can easily compute some basic computation on two numbers. The operation on these two numbers depends on the input is given to `readline()`

function and the expression in switch. The operator value from `readline()`

is matched with the options (cases) in the switch statement and results are displayed when matched.

Consider another example, for different probability, the area under the curve for a F-curve can be selected using the switch as given below.

# q contains the probability under the curve for a F-curve q <- c(0.25, 0.5, 0.75, 0.999) test = 3 v1 = 10 v2 = 20 switch(test, "1" = print (qf(q[1], df1=v1, df2=v2, lower.tail = T) ), "2" = print (qf(q[2], df1=v1, df2=v2, lower.tail = T) ), "3" = print (qf(q[3], df1=v1, df2=v2, lower.tail = T) ), "4" = print (qf(q[4], df1=v1, df2=v2, lower.tail = T) ) )

The code above will produce F-table values for different probability values.