fit_spectral.m

function [ spr g ] = fit_spectral( spr , ref_spr , freq , varargin)
%[ spr g ] = fit_spectral( ref_spr , spr , freq )
%   move spr along the gain axis such that the the squared difference
%   between ref_spr and spr is minimized.
%
%   Arguments:
%      ref_spr: n-by-channels matrix that stores the reference spectra
%      spr:     n-by-channels matrix that stores the movable spectra
%      freq:    a n-by-1 vector that stores the frequancies.
%
%   Returns:
%      spr: the fitted spectra.
%      g: 1-by-channels vector that stores the differences the new spr 
%         and the old one.


p = inputParser ;
p.addParamValue( 'freq_limit' , [min_freq max_freq] , @(x)isnumeric(x) ) ;
p.addParamValue( 'model' , 'add' , @(x)strcmpi(x,'add') || ... 
    strcmpi(x,'mult')  ) ;

p.parse( varargin{:} );

fl = p.Results.freq_limit ;

r = find( freq > fl(1) & freq < fl(2) ) ;

if strcmpi( p.Results.model , 'add' )
    g = -sum( spr(r,:) - ref_spr(r,:) ) / size( spr(r) , 2 ) ;
    
    for i=1:size(spr,2)
        spr(:,i) = spr(:,i) + g(1,i) ;
    end
else
    g = sum( ref_spr.*spr ) / ( sum( spr.^2 ) ) ;
    spr = g*spr ;
end

end