function Hst = modwt_wavelet_sgf(f, wtfname, j)% modwt_wavelet_sgf -- Calculate squared gain function for MODWT wavelet filter.%%****f* wmtsa.dwt/modwt_wavelet_sgf%% NAME%   modwt_wavelet_sgf -- Calculate squared gain function for%     specified MODWT scaling filter at frequencies f and at (optionally) jth level.%% SYNOPSIS%   Hst   = modwt_wavelet_sgf(f, wtfname)%   Hst_j = modwt_wavelet_sgf(f, wtfname, j)%% INPUTS%   f            = vector of sinsuoidal frequency.%   wtfname      = name of a WMSTA-supported MODWT scaling filter.%   j            = (optional) level (index) of scale.%% OUTPUTS%   Hst          = vector of squared gain function values for MODWT wavelet%                  filter h at frequencies f.%   Hst_j        = vector of squared gain function values for MODWT wavelet%                  filter h at frequencies f at jth level.%% SIDE EFFECTS%%% DESCRIPTION%%% EXAMPLE%%% NOTES%%% ALGORITHM%   See page 163 of WMTSA for Hst.%   See page 202 of WMTSA for Hst_j.%%% REFERENCES%   Percival, D. B. and A. T. Walden (2000) Wavelet Methods for%     Time Series Analysis. Cambridge: Cambridge University Press.%% SEE ALSO%   modwt_wavelet_transfer_function%% AUTHOR%   Charlie Cornish%% CREATION DATE%   2003-10-08%% COPYRIGHT%%% REVISION%   $Revision: 612 $%%***% $Id: modwt_wavelet_sgf.m 612 2005-10-28 21:42:24Z ccornish $    usage_str = ['Usage:  [Hst] = ', mfilename, ...               '(f, wtfname, [j])'];  %%  Check input arguments and set defaults.  error(nargerr(mfilename, nargin, [2:3], nargout, [0:1], 1, usage_str, 'struct'));  if (nargin > 2)    error(argterr(mfilename, j, 'posint', [], 1, '', 'struct'));  end  if (exist('j', 'var'))    Ht = modwt_wavelet_transfer_function(f, wtfname, j);  else    Ht = modwt_wavelet_transfer_function(f, wtfname);  end    Hst = Ht .* conj(Ht);  return