fftwtools (version 0.9-11)

fftw: Compute fft using fftw3

Description

These functions compute the FFT using the FFTW3 libraries. Use fftw_r2c(x, HermConj=0) for real to complex fft. This will return the result without the redundant complex conjugate. This follows the R convention for returning the unscaled inverse of the FFT. The function fftw_c2r(res, HermConj=0, n=length(x)) will invert the FFT from the result not containing the redundant complex conjugate. You must specify, n, the dimension of the original data--length--if the redundant complex conjugate is not included.

Usage

fftw(data, inverse=0, HermConj=1, n=NULL)
fftw(data, inverse=0, HermConj=1, n=NULL)
fftw_r2c(data, HermConj=1)
fftw_c2c(data, inverse=0)
fftw_c2r(data, HermConj=1, n=NULL)

Arguments

data

(complex or real) vector to be processed

inverse

(integer) 1 or 0 indicating if inverse FFT is preformed. The return follows the format of the R FFT commands--the output is not scaled.

HermConj

(integer) 1 or 0 indicating if either "Hermitian" redundant conjugate should be returned, or that the complex to real data includes the "Hermitian" redundant conjugate.

n

(integer) column length of the original data set. This is required when using the inverse complex to real FFT without providing the "Hermitian" redundant conjugate.

Examples

# NOT RUN {
res <- fftw_r2c(1:9)
res
fftw_c2r(res)/9
res
fftw_c2r(res)/9

res <- fftw_r2c(1:10)
res
fftw_c2r(res)/10
res
fftw_c2r(res)/10

res <- fftw_r2c(1:9, HermConj=0)
res
fftw_c2r(res, HermConj=0, n=9)/9

res <- fftw_r2c(1:10, HermConj=0)
res
fftw_c2r(res, HermConj=0, n=10)/10

fftw_r2c(1:3)
fftw_c2r(fftw_r2c(1:3))/3
fftw_c2r(fftw_r2c(1:2))/2
fftw_c2r(fftw_r2c(1:4))/4


fftw_r2c(1:3, HermConj=1)
fftw_c2r(fftw_r2c(1:3, HermConj=0), HermConj=0, n=3)/3

fftw_c2r(fftw_r2c(1:4, HermConj=0), HermConj=0, n=4)/4
fftw_c2r(fftw_r2c(1:20, HermConj=0), HermConj=0, n=20)/20

# }