Relational Operators in R

In this tutorial you will learn about the *Relational operators* (also known as **comparison operators**) in R and how to use them. Like most of the programming languages, R programming also has relational operators to check the relationship between two operands. If the relation is true, then it returns the logical value *TRUE*; if the relation is false, then it returns the logical value *FALSE*.

## Relational Operators in R

Following symbols are used as relational operators in R programming language:

Operator Symbols |
Relational Operation |
Example |
---|---|---|

$==$ | Is Equal | $10 == 5$ returns `FALSE` |

$!=$ | Is Not equal | $10 != 5$ returns `TRUE` |

$<$ | Is Less than | $10 < 5$ returns `FALSE` |

$>$ | Is Greater than | $10 > 5$ returns `TRUE` |

$<=$ | Is Less than or equal | $10 <= 5$ returns `FALSE` |

$>=$ | Is Greater than or equal | $10 >= 5$ returns `TRUE` |

Note than the output of relational operation contains the boolean values (`TRUE`

or `FALSE`

) based on the relational operator.

## Examples of Relational Operators

To understand the use of relational operators, let us discuss some examples.

### Equal to

`10 == 5`

`[1] FALSE`

Above R command check whether 10 equal to 5. Since 10 is not equal to 5, R returns FALSE.

### Not Equal to

`10 != 5`

`[1] TRUE`

Above R command check whether 10 is not equal to 5. Since 10 is not equal to 5, R returns TRUE.

### Less Than

`10 < 5`

`[1] FALSE`

Above R command check whether 10 is less than 5. Since 10 is not less than 5, R returns FALSE.

### Greater Than

`10 > 5`

`[1] TRUE`

Above R command check whether 10 is greater than 5. Since 10 is greater than 5, R returns TRUE.

### Less Than or Equal

`10 <= 5`

`[1] FALSE`

Above R command check whether 10 less than or equal to 5. Since 10 is not less than or equal to 5, R returns FALSE.

### Greater Than or Equal

`10 >= 5`

`[1] TRUE`

Above R command check whether 10 greater than or equal to 5. Since 10 is greater than or equal to 5, R returns TRUE.

## Relational operations on Vector and scalar

Like arithmetic operators, relational operations are also vectorized. When vector is compared with scalar using relational operator, R will recycled the scalar element to the length of vector and then perform element-wise relational operations.

```
# Create a vector x
x <- c(12, 10, 8, 16, 6)
x < 8
```

`[1] FALSE FALSE FALSE FALSE TRUE`

`x == 10`

`[1] FALSE TRUE FALSE FALSE FALSE`

`x <= 8`

`[1] FALSE FALSE TRUE FALSE TRUE`

Note than in all the above R codes, the left side of relational operator is a vector and right side of is a scalar. In such a case R recycle the scalar to match the length of vector and then perform the element-wise relational operation.

Relational operators can also be used to extract the elements of a vector based on some relational expression.

Suppose we need to extract only those elements of `x`

which are less than 8. To do this we can use following R code:

```
x <- c(12, 10, 8, 16, 6)
x[x > 8]
```

`[1] 12 10 16`

Above code extract only those elements of `x`

which are greater than 8.

`x[x != 10]`

`[1] 12 8 16 6`

Above code extract only those elements of `x`

which are not equal to 10.

`x[x <= 8]`

`[1] 8 6`

Above code extract only those elements of `x`

which are less than or equal to 8.

## Relational operations on Vectors of equal length

If the length of both the operand in relational expression is same, R will check the relation element-wise.

```
x <- c(12, 10, 8, 16, 6)
y <- c(10, 12, 8, 18, 6)
```

```
# Are x and y equal (element-wise)?
x == y
```

`[1] FALSE FALSE TRUE FALSE TRUE`

```
# Are x less than equal to y-2 (element-wise)?
x <= y - 2
```

`[1] FALSE TRUE FALSE TRUE FALSE`

## Relational operations on Vectors of unequal length

Recycling rule also work while comparing a shorter vector with a longer vector. R will recycle the elements of shorter vector and then perform the relational operation element-wise.

```
x <- c(10, 20, 6, 25)
y <- c(4, 20, 8)
```

As `y`

is shorter than `x`

, R will recycled the elements of shorter vector `y`

as `(4,20,8,4)`

and then perform the relational operations element-wise.

```
# Are x and y equal (element-wise)?
x == y
```

```
Warning in x == y: longer object length is not a multiple of shorter object
length
```

`[1] FALSE TRUE FALSE FALSE`

```
# Are x less than y (element-wise)?
x < y
```

```
Warning in x < y: longer object length is not a multiple of shorter object
length
```

`[1] FALSE FALSE TRUE FALSE`

```
# Are x less than or equal to y (element-wise)?
x <= y
```

```
Warning in x <= y: longer object length is not a multiple of shorter object
length
```

`[1] FALSE TRUE TRUE FALSE`

```
# Are x not equal to y (element-wise)?
x != y
```

```
Warning in x != y: longer object length is not a multiple of shorter object
length
```

`[1] TRUE FALSE TRUE TRUE`

Note than the output of relational operation on vectors will be another vector of same length and will contain the boolean values (`TRUE`

or `FALSE`

) based on the element-wise comparison.

## Endnote

In this tutorial you learned about relational operators in R and how R uses recycling rule while performing relational operations.

To learn more about other operators in R, please refer to the following tutorials:

Assignment operators in R

Arithmetic operators in R

Logical operators in R

Miscellaneous operators in R

Precendence of Operators in R

Operators in R

Hopefully you enjoyed learning this tutorial on relational operators in R. Hope the content is more than sufficient to understand relational operators in R.