function Gs = dwt_scaling_sgf(f, wtfname, j)% dwt_scaling_sgf -- Calculate squared gain function for DWT scaling filter.%%****f* wmtsa.dwt/modwt_scaling_sgf%% NAME%   modwt_scaling_sgf -- Calculate squared gain function for%     frequencies f for specified DWT scaling filter and (optionally) jth level.%% SYNOPSIS%   Gs_j = dwt_scaling_sgf(f, wtfname, [j])%% INPUTS%   f            = vector of sinsuoidal frequency.%   wtfname      = name of a WMSTA-supported DWT scaling filter.%   j            = (optional) level (index) of scale.%% OUTPUTS%   Gs           = vector of squared gain function values for DWT scaling filter h%                  at frequencies f.%   Gs_j         = vector of squared gain function values for DWT scaling filter h%                  at frequencies f at jth level.%% SIDE EFFECTS%%% DESCRIPTION%%% EXAMPLE%%% NOTES%%% ALGORITHM%   See page  76 of WMTSA for Gs.%   See page 154 of WMTSA for Gs_j.%% REFERENCES%   Percival, D. B. and A. T. Walden (2000) Wavelet Methods for%     Time Series Analysis. Cambridge: Cambridge University Press.%% SEE ALSO%   dwt_scaling_transfer_function%% AUTHOR%   Charlie Cornish%% CREATION DATE%   2003-10-08%% COPYRIGHT%%% REVISION%   $Revision: 612 $%%***% $Id: dwt_scaling_sgf.m 612 2005-10-28 21:42:24Z ccornish $    usage_str = ['Usage:  [Gs] = ', 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'))    G = dwt_scaling_transfer_function(f, wtfname, j);  else    G = dwt_scaling_transfer_function(f, wtfname);  end    Gs = G .* conj(G);  return