function H=tanh_taper(npts)
%  Function TANH_TAPER
%   
% computes a smooooooth taper verifying :
%   - H(1) = 0
%   - H(npts) = 1  (almost)
%  based on the functional form of the hyperbolic tangent
%  
 %   inputs : number of points (npts)
%   JEG, Jan 2005   
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
    t=linspace(0,1,npts);
    H=(1+tanh((t-.5)*2*pi))/2;
    % note, the 2*pi constant is here for the fun. Between 3 and 3.5 works well