IsPrime Property

Returns for a vector or matrix of positive integers a logical object of the same dimension(s) containing TRUE for the elements that are prime and FALSE otherwise.

IsPrime(x)

Arguments

x

vector or matrix of nonnegative integers

Details

Given a vector or a matrix of positive integers returns a vector of the same size of FALSE and TRUE. Use which(IsPrime(1:21)) to get the positions.

Value

logical vector

Author

Hans W. Borchers <hwborchers@googlemail.com>

See also

Factorize, 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(IsPrime(octett))) {
        cat(octett, "\n", sep="  ")
        break
    }
}
#> 1006301  1006303  1006307  1006309  1006331  1006333  1006337  1006339