pracma (version 1.7.3)

isprime: isprime Property

Description

Vectorized version, returning for a vector or matrix of positive integers a vector of the same size containing 1 for the elements that are prime and 0 otherwise.

Usage

isprime(x)

Arguments

x

vector or matrix of nonnegative integers

Value

• array of elements 0, 1 with 1 indicating prime numbers

Details

Given an array of positive integers returns an array of the same size of 0 and 1, where the i indicates a prime number in the same position.

See Also

factors, primes

Examples

x <- matrix(1:10, nrow=10, ncol=10, byrow=TRUE)
  x * isprime(x)

  # Find first prime number octett:
  octett <- c(0, 2, 6, 8, 30, 32, 36, 38) - 19
  while (TRUE) {
      octett <- octett + 210
      if (all(as.logical(isprime(octett)))) {
          cat(octett, "", sep="")
          break
      }
  }