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testnfreq(nfreq), nfreq a vector of positive integers

Keywords: fourier transforms
testnfreq(nfreq) returns a LOGICAL vector the same length as nfreq, a
vector of positive integers.  Element j of the result is True if and
only if nfreq[j] has no prime factors > 29.

testnfreq() is useful in macros which use one of the fast Fourier
transform functions, rft(), dft() and hft(), since these operate only on
vectors or matrices x for which nrows(x) has no prime factors > 29.  It
allows you to test whether this condition is true.

The use of testnfreq() is deprecated since goodfactors() can be used in
an equivalent test.  When N is a scalar, goodfactors(N) == N is True if
and only if testnfreq(N) is true.  Moreover, the value of goodfactors(N)
is the next integer >= N with no prime factors > 29.

  if (!testnfreq(nrows(y))){
    error("nrows(y) has prime factor > 29")
    yft <- rft(y)

See also topics goodfactors(), primefactors(), rft(), hft(), cft(),

Gary Oehlert 2003-01-15