function s = getlevel( w, level )
% FUNCTION:    getlevel
%
% SYNOPSIS:    S = getlevel( W, LEVEL )
%
% DESCRIPTION: Function getlevel returns in S those wavelet
%              coefficients, from coefficient vector W, 
%              at the level specified in the integer LEVEL.
%              Level number -1 refers to the first element of
%              W. Level number k ( integer greater than -1 )
%              refers to w( 2^k + [1:2^k] ). If w is a column 
%              (row) S is a column (row).
%
% EXAMPLE: w = [1:8]
%           w =
%                1     2     3     4     5     6     7     8
%          getlevel(w,1)
%           ans =
%                3     4 
%

%
% AUTHOR: Neil Getz
% DATE: 5-4-92
%
% COPYRIGHT 1992, Neil Getz
%

if(nargin < 2),
  help getlevel;
  return;
end
p = log(length(w))/log(2);
if( rem(p,1) ~= 0 ),
  error('getlevel: The length of arg 1 must be a positive power of 2.');
end

if( sum(rem(level,1)) ~= 0 ) ,
  error('getlevel: arg 2 must contain only integers >= -1');
end;

if(p <= level),
  error('level number too high for this coordinate vector.');
end;

if ( level == -1 ),
    s = w(1);
  else
    s = w( 2^level + [1:2^level] );
end