Control Statements in R

Control Statements in R

Control statements in programming are used to dictate the flow of execution based on certain conditions or loops. R, like other programming languages, offers a suite of control statements to facilitate this. This tutorial will cover the basics of control statements in R, including conditional statements and loops.

1. Conditional Execution

a. if statement:

The basic if statement checks a condition and executes the associated code block if the condition is TRUE.

x <- 5 if (x > 0) { print("x is positive") }

b. if-else statement:

Adds an alternative action if the initial if condition is FALSE.

if (x > 0) { print("x is positive") } else { print("x is non-positive") }

c. if-else if-else statement:

Allows checking multiple conditions sequentially.

if (x > 0) { print("x is positive") } else if (x < 0) { print("x is negative") } else { print("x is zero") }

2. Switch Statement

The switch statement is used to execute one block of code from multiple conditions:

y <- "b" result <- switch(y, a = "You chose A", b = "You chose B", c = "You chose C", "Unknown choice" ) print(result)

3. Loops

a. for loop:

Used for iterating over a sequence (vector, list).

for (i in 1:5) { print(i) }

b. while loop:

Keeps running as long as the condition is TRUE.

count <- 1 while (count <= 5) { print(count) count <- count + 1 }

c. repeat loop:

An infinite loop that only breaks when a break statement is encountered.

count <- 1 repeat { print(count) if (count >= 5) { break } count <- count + 1 }

4. Controlling Loop Execution

a. next:

Skips the current iteration and proceeds to the next.

for (i in 1:5) { if (i == 3) { next } print(i) }

b. break:

Exits the loop immediately.

for (i in 1:5) { if (i == 4) { break } print(i) }

Summary:

Control statements in R, such as conditional statements (if-else) and loops (for, while, and repeat), offer flexibility in code execution based on specified conditions. By understanding and using these constructs effectively, you can create dynamic and adaptable R scripts.

Examples

  1. If-Else Statements in R:

    Use if-else statements for conditional execution.

    # If-else statements in R x <- 10 if (x > 0) { print("Positive") } else { print("Non-positive") }

  2. Switch Statement in R:

    Implement switch statements for multiple conditions.

    # Switch statement in R day <- "Monday" message <- switch(day, "Monday" = "Start of the week", "Friday" = "End of the week", "Default message") print(message)

  3. For Loop in R:

    Use for loops for iterative tasks.

    # For loop in R for (i in 1:5) { print(paste("Iteration", i)) }

  4. While Loop in R:

    Implement while loops for repetitive tasks.

    # While loop in R i <- 1 while (i <= 5) { print(paste("Iteration", i)) i <- i + 1 }

  5. Repeat and Break Statements in R:

    Utilize repeat and break statements for indefinite loops.

    # Repeat and break statements in R i <- 1 repeat { print(paste("Iteration", i)) i <- i + 1 if (i > 5) break }

  6. Conditional Execution in R Programming:

    Execute code conditionally based on logical conditions.

    # Conditional execution in R programming x <- 10 if (x > 0) { print("Positive") }

  7. Nested Control Statements in R:

    Nest control statements for complex logic.

    # Nested control statements in R for (i in 1:3) { for (j in 1:3) { print(paste("Nested Iteration", i, j)) } }

  8. Control Flow in R:

    Manage control flow using a combination of statements.

    # Control flow in R x <- 10 if (x > 0) { print("Positive") } else { print("Non-positive") }

  9. Error Handling Within Control Statements in R:

    Handle errors within control statements using tryCatch().

    # Error handling within control statements in R tryCatch({ x <- 1 / 0 print(x) }, error = function(e) { print(paste("Error:", e$message)) })

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