function wavelet_coefs  = dwt(data,H,level)
% =======================================
% function  wavelet_coefs  = dwt(data,H,level) calculates the
% DWT of periodized data by using filter H. 
% The depth of the transformation is 'level'
% ============= STA 293 =================
n = length(H);  N = length(data);
if nargin==2, level = round(log10(N)/log10(2)); end;
C = data; 
D = [];
G =  fliplr(H);  G(1:2:n) = -G(1:2:n);              % Quadrature Mirror
for j = 1:level                                     % Mallat's algorithm
   N = length(C);
   C = [C C];                                       % Make periodic
   d = filter(G, 1, C);                             % Convolve                    
   d =d(2:2:N);                                     % Downsample
   D = [d,D];                                       % Concatenate 
   C = filter(H, 1, C);                             % Convolve
   C =C(2:2:N);                                     % Downsample
end;                                                %
wavelet_coefs = [C,D];                              % DWT
%========================================================================