Example of standard logical operations

Truth table

> x = TRUE

> y = FALSE

> x & y # x AND y

[1] FALSE

> x | y # x OR y

[1] TRUE

> !x # negation of x

[1] FALSE

Example

> x <- 5

> Logical1 <- (x > 2)

> is.logical (Logical1)

[1] TRUE

> Logical2 <- (x < 10)

> is.logical (Logical2)

[1] TRUE

Example

> x <- 5

> Logical3 <- (2*x > 11)

> is.logical (Logical3)

[1] TRUE

> Logical4 <- (3*x <20)

> is.logical (Logical4)

[1] TRUE

Control structures in R :

control statements,

loops,

function

Conditional execution

1. Conditional execution

Syntax

if (condition) {executes commands if condition is TRUE}

if (condition) {executes commands if condition is TRUE}

else {executes commands if condition is FALSE}

please note:

> x <- 5

> if ( x == 3) { x <- x-1} else { x <- 2*x}

Interpretation:

> x

[1] 10

Now choose x = 3 and repeat this example

Truth table

> x = TRUE

> y = FALSE

> x & y # x AND y

[1] FALSE

> x | y # x OR y

[1] TRUE

> !x # negation of x

[1] FALSE

Example

> x <- 5

> Logical1 <- (x > 2)

> is.logical (Logical1)

[1] TRUE

> Logical2 <- (x < 10)

> is.logical (Logical2)

[1] TRUE

Example

> x <- 5

> Logical3 <- (2*x > 11)

> is.logical (Logical3)

[1] TRUE

> Logical4 <- (3*x <20)

> is.logical (Logical4)

[1] TRUE

Control structures in R :

control statements,

loops,

function

Conditional execution

1. Conditional execution

Syntax

if (condition) {executes commands if condition is TRUE}

if (condition) {executes commands if condition is TRUE}

else {executes commands if condition is FALSE}

please note:

- The condition in this control statement may not be vector valued and if so, only the first element of the vector is used.
- The condition may be complex expression where the logical operators "and" (&&) and "or" (| |) can be used.

> x <- 5

> if ( x == 3) { x <- x-1} else { x <- 2*x}

Interpretation:

- If x = 3, then execute x = x - 1.
- If x ≠ 3, then execute x = 2*x.

> x

[1] 10

Now choose x = 3 and repeat this example

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