WZIP(1) 						      General Commands Manual							   WZIP(1)

NAME

       wzip - lossy data compression and denoising

SYNOPSIS

       wzip [ -c | -d | -dn | -hdn ] num sf

DESCRIPTION

       This manual page documents the wzip command.

       wzip is a program that can be used for LOSSY data compression and denoising.  It reads from STDIN and writes to STDOUT. In compression mode
       the input is a sequence of ascii floating-point values.	num is the number of these data values. The output is a sequence  of  small  inte-
       gers,  most of them zero in typical application. This is ready for effective compression with a standard loss-less compression program like
       gzip.

       The program can also be used for denoising. In this case both input and output are sequences of ascii floating-point values.

       The scale factor sf determines the strength of compression or denoising.  A higher scale factor	means  heavier	compression  and  stronger
       denoising.   Four  times  the standard deviation of the noise content is a good start.  Otherwise 5 percent of the overall signal amplitude
       might be used as a first estimation of a suitable scale factor.

       If the noise content of the input data is strongly non-Gaussian-distributed, like Poisson noise. The input data should  be  transformed	to
       approximate  Gaussian-distributed  noise. If the input values are Poisson-distributed, that means for example raw counts per channel in EDX
       or XPD, they can be transformed to approximate Gaussian-distributed noise by transformation of each data point with y:=2.0*sqrt(x+0.25109).
       Back  transformation is done with y:=(x/2)^2. The summand 0.25109 compensates for the bias caused by the asymmetry of the Poisson-distribu-
       tion.

       Invoking the program without any options writes examples of the use of the program to STDERR.

OPTIONS

       There must be given exactly one option.

       -c     Compression, reads num ascii floating-point values from STDIN and writes a sequence of integers with high redundancy to STDOUT.

       -d     Decompression, reads from STDIN and writes a sequence of num ascii floating-point values to STDOUT. These are more or  less  similar
	      to the original data.

       -dn    Denoising,  reads  num  ascii  floating-point  values from STDIN and writes a sequence of num ascii floating-point values to STDOUT.
	      These are more or less similar to the original data.

       -hdn   Denoising with hard thresholding instead of wavelet shrinkage. Single untouched noise peaks may be visible with this  mode.  On  the
	      other hand, there is much less impact on the signal slope.

SEE ALSO

       Donoho,	D.L.; Johnstone, I.M.: Adapting to unknown smoothness via wavelet shrinkage, technical report 425, Department of Statistics, Stan-
       ford University, Stanford, June 1993, ftp://playfair.stanford.edu/pub/donoho/ausws.ps.Z

       Franzen, A.: Compression of process data with a wavelet method, steel res. 69 (1998), No. 1, pp. 28/30

       Franzen, A.: Non-linear denoising with wavelet transformation, Z. Metallkd.  89 (1998), No. 4, pp. 297/302

AUTHOR

       This manual page was written by Andreas Franzen <anfra@debian.org>, for the Debian GNU/Linux system (but may be used by others).

       Copyright (C) 1997 Andreas Franzen, placed under the GNU General Public License, see the file copyright for details.

								 24 December 1997							   WZIP(1)