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rft(rx [,divbyT:T]), rx a REAL matrix

Keywords: time series, complex arithmetic
rft(rx) where rx is a REAL vector or matrix, computes the Hermitian form
of the complex discrete Fourier transform of each column of rx,
considered as a real series.

Any MISSING values in rx are replaced by 0 in computing the result and a
warning message is printed.

rft(rx,divbyt:T) does the same except the result is divided by the
number of rows of rx.

hft(hconj(hx),divbyt:T) is the inverse of rft() in the sense that rx and
hft(hconj(rft(rx)),divbyt:T) are equal except for rounding error.

The largest prime factor of nrows(rx) must not exceed 29.  You can use
primefactors() to find the maximum factor of nrows(rx) and goodfactors()
to find a length >= nrows(rx) which has no prime factors > 29.  In
addition, the product of all the "unpaired" prime factors can't be too
large.  For example N = 3*5*7*11*13*17*M^2 = 255255*M^2, where M is an
integer, breaks the algorithm and hence is not allowed.

See topic 'complex' for discussion of complex matrices in MacAnova.

See also cft(), hft(), hconj(), primefactors(), goodfactors().

Gary Oehlert 2003-01-15