isprime Property

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.

isprime(x)

Arguments

x

vector or matrix of nonnegative integers

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.

Value

array of elements 0, 1 with 1 indicating prime numbers

See also

factors, primes

Examples

  x <- matrix(1:10, nrow=10, ncol=10, byrow=TRUE)
  x * isprime(x)
#>       [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
#>  [1,]    0    2    3    0    5    0    7    0    0     0
#>  [2,]    0    2    3    0    5    0    7    0    0     0
#>  [3,]    0    2    3    0    5    0    7    0    0     0
#>  [4,]    0    2    3    0    5    0    7    0    0     0
#>  [5,]    0    2    3    0    5    0    7    0    0     0
#>  [6,]    0    2    3    0    5    0    7    0    0     0
#>  [7,]    0    2    3    0    5    0    7    0    0     0
#>  [8,]    0    2    3    0    5    0    7    0    0     0
#>  [9,]    0    2    3    0    5    0    7    0    0     0
#> [10,]    0    2    3    0    5    0    7    0    0     0

  # 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, "\n", sep="  ")
          break
      }
  }
#> 1006301  1006303  1006307  1006309  1006331  1006333  1006337  1006339