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    %% Level 3 Approximation Coefficients
% This example shows how to extract the level 3 approximation coefficients.
%%
% Load the signal consisting of electricity usage data.

% Copyright 2015 The MathWorks, Inc.

load leleccum; 
sig = leleccum(1:3920); 
%%
% Obtain the DWT down to level 5 with the |'sym4'| wavelet.
[C,L] = wavedec(sig,5,'sym4');
%%
% Extract the level-3 approximation coefficients. Plot the original signal
% and the approximation coefficients.
Lev = 3;
a3 = appcoef(C,L,'sym4',Lev);
subplot(2,1,1)
plot(sig); title('Original Signal');
subplot(2,1,2)
plot(a3); title('Level-3 Approximation Coefficients');
%%
% You can substitute any value from 1 to 5 for |Lev| to obtain the
% approximation coefficients for the corresponding level.