ldacorr(3)

LIBRARY ROUTINE
ldacorr - Autocorrelation sequence of 1-D signal(s)

LIBRARY CALL
#include "vinclude.h"
int
ldacorr ( image, arith_type, out_option, points, process_dir )
int out_option, arith_type, points, process_dir;
struct xvimage *image;

INPUT

image
    pointer to VIFF structure containing image data to be processed.

procdir
    process direction: 0 indicated vector oriented processing, 1 indicates band oriented processing.

OUTPUT

image
    pointer to VIFF structure containing image data after processing.

Return Value:
    1 on success, 0 on failure.

MODIFICATIONS

Jeremy Worley 7 Jun 1990 14:31 MST
    added error checking to all memory allocations

Jeremy Worley 19 Jul 19 1990 16:27 MST
    changed apoints to dpoints in minor loop of ldtacorr for both real and complex parts to conform to proper definition of autocorrelation.

Jeremy Worley 17 Feb 1992 10:16 MST
    changed call to lfft1d in ldfacorr() to fft842_() since lfft1d is being phased out. Also cleaned up some implicitly defined functions and modularized ldfacorr() which resulted in the creation of a static function called _lfacorr(). Also fixed a small scaling problem with the output of ldfacorr().

Jeremy Worley 09 Mar 1992 19:54 MST
    Deleted a declaration to cdiv() since it was not used.

DESCRIPTION
1D Autocorrelation Estimate. Generates the biased, unbiased or FFT based autocorrelation estimate of a data sequence. It can operate on Real and Complex data. If complex data, the user has the option of using complex arithmetic (vector) or real arithmetic (scalar = treat the real number and imaginary number independently). NOTE: complex data is expected to be in rectangular (not polar) form.
      The autocorrelation function is a symmetric function,
      thus, only one side of the sequence is generated.

dacorr does not work on explicit location data and will return an error when such a file is encountered. No output file will be created. dacorr works only on VFF_TYP_FLOAT or VFF_TYP_COMPLEX data files.

Input/Output Files

The input file must be of type VFF_TYP_FLOAT or VFF_TYP_COMPLEX. The output file returned will be of size specified by the user. If the data is of type VFF_TYP_COMPLEX and complex aithmetic is selected then the output file will be of type VFF_TYP_FLOAT. *********************************************************************

The autocorrelation default option is the -g (biased estimate = 0) option. When this option is selected, dacorr calculates the biased autocorrelation estimate.

Process direction

Data can be processed with either band or vector orientation (-d option). The default data processing direction is in the vector direction (-d = 0). This means that data stored in multiband format will be processed as a set pixel location. The direction of processing can be changed so that each band is processed as a signal (instead of each vector being a signal) by setting the -d option to 1.

SEE ALSO
dacorr(1), intro(3), vipl(3), verror(3), vutils(3)

RESTRICTIONS
works only on VFF_TYP_COMPLEX and VFF_TYP_FLOAT.

dacorr does not work on explicit location data and will return an error when such a data file is encountered.

AUTHOR
Ramiro Jordan, Jeremy Worley

COPYRIGHT
Copyright 1992, University of New Mexico. All rights reserved.