(This article was first published on

**Xi'an's Og » R**, and kindly contributed to R-bloggers)**N**eil Gunther has pointed out on his blog that the prime number decomposition R package schoolmath contains mistakes in the function primes, listing 1 as a prime number but also including decomposable numbers like 133 in its list of prime numbers:

> primes(100,140)

[1] 101 107 111 113 123 129 131 137

> primes(50,140)

[1] 51 53 59 61 67 71 73 79 83 89 97 101 103 107 109 113 127 131133

[20] 137 139

> is.prim(primes(133)

[1]FALSE

> is.prim(primes(200,300))

[1]FALSETRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUEFALSETRUE

[13] TRUE TRUE TRUE TRUE TRUE TRUE

> sum(1-is.prim(primes(1,1000)))

[1]10

> data(primlist)

> sum(1-is.prim(primlist[1:25000]))

[1]3309

**T**his is rather annoying and I hope it gets quickly fixed!

Filed under: R Tagged: bug, prime factor decomposition, prime numbers, R, schoolmath

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