01-06-2010
sed -i 's/^/Root /g' a.txt
-i option will do inplace modification.
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LEARN ABOUT REDHAT
pdl::fft
FFT(3) User Contributed Perl Documentation FFT(3)
NAME
PDL::FFT - FFTs for PDL
DESCRIPTION
FFTs for PDL. These work for arrays of any dimension, although ones with small prime factors are likely to be the quickest.
Each routine works `inplace'.
SYNOPSIS
use PDL::FFT qw/:Func/;
fft($real,$imag);
ifft($real,$imag);
realfft($real);
realifft($real);
fftnd($real,$imag);
ifftnd($real,$imag);
$kernel = kernctr($image,$smallk);
fftconvolve($image,$kernel);
ALTERNATIVE FFT PACKAGES
Various other modules - such as PDL::FFTW and PDL::Slatec - contain FFT routines. However, unlike PDL::FFT, these modules are optional,
and so may not be installed.
FUNCTIONS
fft
Signature: ([o,nc]real(n); [o,nc]imag(n))
Complex FFT of the "real" and "imag" arrays [inplace]
ifft
Signature: ([o,nc]real(n); [o,nc]imag(n))
Complex Inverse FFT of the "real" and "imag" arrays [inplace]
realfft()
One-dimensional FFT of real function [inplace].
The real part of the transform ends up in the first half of the array and the imaginary part of the transform ends up in the second half of
the array.
realfft($real);
realifft()
Inverse of one-dimensional realfft routine [inplace].
realifft($real);
fftnd()
N-dimensional FFT (inplace)
fftnd($real,$imag);
ifftnd()
N-dimensional inverse FFT
ifftnd($real,$imag);
fftconvolve()
N-dimensional convolution
$kernel = kernctr($image,$smallk);
fftconvolve($image,$kernel);
fftconvolve works inplace, and returns an error array in kernel as an accuracy check -- all the values in it should be negligible.
The sizes of the image and the kernel must be the same. kernctr centres a small kernel to emulate the behaviour of the direct convolution
routines.
The speed cross-over between using straight convolution (PDL::Image2D::conv2d()) and these fft routines is for kernel sizes roughly 7x7.
kernctr()
`centre' a kernel (auxiliary routine to fftconvolve)
$kernel = kernctr($image,$smallk);
fftconvolve($image,$kernel);
kernctr centres a small kernel to emulate the behaviour of the direct convolution routines.
convmath
Signature: ([o,nc]a(m); [o,nc]b(m))
Internal routine doing maths for convolution
cmul
Signature: (ar(); ai(); br(); bi(); [o]cr(); [o]ci())
Complex multiplication
cdiv
Signature: (ar(); ai(); br(); bi(); [o]cr(); [o]ci())
Complex division
BUGS
Where the source is marked `FIX', could re-implement using phase-shift factors on the transforms and some real-space bookkeeping, to save
some temporary space and redundant transforms.
AUTHOR
This file copyright (C) 1997, 1998 R.J.R. Williams (rjrw@ast.leeds.ac.uk), Karl Glazebrook (kgb@aaoepp.aao.gov.au), Tuomas J. Lukka,
(lukka@husc.harvard.edu). All rights reserved. There is no warranty. You are allowed to redistribute this software / documentation under
certain conditions. For details, see the file COPYING in the PDL distribution. If this file is separated from the PDL distribution, the
copyright notice should be included in the file.
perl v5.8.0 2003-01-29 FFT(3)