% LORENTZ_LSHAPE   Different versions of pressure broadened line shape
%
%    Calculates different versions of the pressure induced line shape. The most
%    basic version is denoted as the Lorentz line shape.
%
%    The line shape can be expressed as
%      l = 1/pi * (f/f0)^prefac * ( dp/((f-f0)^2+dp) + dp/((f+f0)^2+dp) )
%    where the second term (including f+f0) is considered only if *mirror*
%    is set.
%
%    Default values correspond to the basic Lorentz shape. The van
%    Vleck-Weisskopf line shape is obtained witj prefac=2 and mirror=true.
%
% FORMAT   l = doppler_lshape( f, f0, dp )
%        
% OUT   l    Line shape. Dimensions [f,dp]. 
% IN    f    Frequency vector.
%       f0   Centre frequency. Only scalar input allowed.
%       dp   Pressure broadened line width. Following standard definition,
%            which corresponds to FWHM/2. Can be a vector. 
% OPT   prefac  Exponent for (f/f0) term. Default is 0.
%       mirror  To consider the mirror transition at -f0. Default is false.

% 2006-11-21   Created by Patrick Eriksson.


function l = lorentz_lshape(f,f0,dp,prefac,mirror)

prefac_DEFAULT = 0;
mirror_DEFAULT = false;
%
set_defaults

  
l = zeros( length(f), length(dp) );

f = vec2col( f );


if prefac == 0
  a = 1/pi;
else
  a = (f/f0).^prefac/pi;
end


for i = 1 : length(dp)

  if mirror
    l(:,i) = a .* ( dp(i) ./ ( (f-f0).^2 + dp(i)^2 ) + ...
                    dp(i) ./ ( (f+f0).^2 + dp(i)^2 ) );
  else
    l(:,i) = a .* ( dp(i) ./ ( (f-f0).^2 + dp(i)^2 ) );
  end
end