WALSH
Walsh and Haar Transforms

WALSH is a FORTRAN77 library which implements versions of the Walsh and Haar transforms.

Note that the programs, as printed in the reference, had a few typographical errors. Several programs, in particular FHT and FRT, could not be made to perform as described in the text, and hence have been omitted.

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages:

WALSH is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

FFTPACK5 is a FORTRAN77 library which implements the Fast Fourier Transform.

HAAR, is a FORTRAN77 library which computes the Haar transform of data.

SFTPACK a FORTRAN77 library which implements the "slow" Fourier transform, intended as a teaching tool and comparison with the fast Fourier transform.

WAVELET, a FORTRAN77 library which does some simple calculations with wavelet transforms;

Reference:

1. Ken Beauchamp,
   Walsh functions and their applications,
   Academic Press, 1975,
   ISBN: 0-12-084050-2,
   LC: QA404.5.B33.

Source Code:

• walsh.f, the source code.
• walsh.sh, BASH commands to compile the source code.

Examples and Tests:

• walsh_prb.f, a sample calling program.
• walsh_prb.sh, BASH commands to compile and run the sample program.
• walsh_prb_output.txt, the output file.

List of Routines:

• FFWT performs an in-place fast Walsh transform.
• FWT performs a fast Walsh transform.
• HAAR performs a Haar transform.
• HAARIN inverts a Haar transform.
• HNORM computes the normalization factors for a forward or inverse Haar transform.
• I4_LOG_2 returns the integer part of the logarithm base 2 of an I4.
• I4_MODP returns the nonnegative remainder of integer division.
• I4_WRAP forces an I4 to lie between given limits by wrapping.
• R8VEC_COPY copies an R8VEC.
• R8VEC_SHIFT_CIRCULAR performs a circular shift on an R8VEC.
• R8VEC_UNIFORM_01 returns a unit pseudorandom R8VEC.
• TIMESTAMP prints out the current YMDHMS date as a timestamp.
• WALSH performs a fast Walsh transform.

You can go up one level to the FORTRAN77 source codes.