| # File src/library/stats/R/fft.R |
| # Part of the R package, https://www.R-project.org |
| # |
| # Copyright (C) 1995-2012 The R Core Team |
| # |
| # This program is free software; you can redistribute it and/or modify |
| # it under the terms of the GNU General Public License as published by |
| # the Free Software Foundation; either version 2 of the License, or |
| # (at your option) any later version. |
| # |
| # This program is distributed in the hope that it will be useful, |
| # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| # GNU General Public License for more details. |
| # |
| # A copy of the GNU General Public License is available at |
| # https://www.R-project.org/Licenses/ |
| |
| fft <- function(z, inverse=FALSE) .Call(C_fft, z, inverse) |
| |
| mvfft <- function(z, inverse=FALSE) .Call(C_mvfft, z, inverse) |
| |
| nextn <- function(n, factors=c(2,3,5)) .Call(C_nextn, n, factors) |
| |
| convolve <- function(x, y, conj=TRUE, type=c("circular","open","filter")) |
| { |
| type <- match.arg(type) |
| n <- length(x) |
| ny <- length(y) |
| Real <- is.numeric(x) && is.numeric(y) |
| ## switch(type, circular = ..., ) |
| if(type == "circular") { |
| if(ny != n) |
| stop("length mismatch in convolution") |
| } |
| else { ## "open" or "filter": Pad with zeros |
| n1 <- ny - 1 |
| x <- c(rep.int(0, n1), x) |
| n <- length(y <- c(y, rep.int(0, n - 1)))# n = nx+ny-1 |
| } |
| x <- fft(fft(x)* (if(conj)Conj(fft(y)) else fft(y)), inverse=TRUE) |
| if(type == "filter") |
| (if(Real) Re(x) else x)[-c(1L:n1, (n-n1+1L):n)]/n |
| else |
| (if(Real) Re(x) else x)/n |
| } |
| |