# Fast Functions for Prime Numbers in R

**Authors**: Os Keyes and Paul Egeler

**License**: MIT

## Description

This R package has several utility functions for dealing with prime numbers, such as checking for primality and generating prime numbers. Additional functions include:

- finding prime factors and Ruth-Aaron pairs
- finding next and previous prime numbers in the series
- finding or estimating the n
^{th} prime
- estimating the number of primes less than or equal to an arbitrary number
- computing primorials
- finding prime k-tuples (e.g., twin primes)
- finding the greatest common divisor and smallest (least) common multiple
- testing whether two numbers are coprime
- computing Eulerâ€™s totient (phi)

The package also provides an R dataset containing the first one thousand primes.

## Installation

You can install the released version of primes from CRAN with:

`install.packages("primes")`

And the development version from GitHub with:

```
# install.packages("devtools")
devtools::install_github("ironholds/primes")
```

## Example

This checks which of the first twenty natural numbers are prime:

```
library(primes)
is_prime(1:20)
## [1] FALSE TRUE TRUE FALSE TRUE FALSE TRUE FALSE FALSE FALSE TRUE FALSE TRUE FALSE
## [15] FALSE FALSE TRUE FALSE TRUE FALSE
```

You can also generate all the prime numbers between 101 and 199 with the following:

```
generate_primes(101, 199)
## [1] 101 103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191 193 197 199
```