function y= interpol2(x)% function y= interpol2(x)%   This file is part of the TFPM toolbox v1.0 (c)%   michael.jachan@tuwien.ac.at and underlies the GPL.% % Interpolates x by 2, filtering?%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%if(0)% TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%clear;tfpm;N    = 128;x= sin(20*pi/N*(0:N-1));%x= randn(N, 1);%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%end;% TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%N= length(x);y1= zeros(2*N, 1);y1(1:2:end)= x;[B, A] = butter(5, .5);y= 2*filter(B, A, y1);%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%if(0)% TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%clear;tfpm;N= 256;x= sin(2*pi/N*(0:N-1))';x= randn(N, 1);KK= 10figure(1);yold= x;for k= 1:KK   ynew= interpol2(yold);   subplot(KK, 1, k)   plot(ynew);axis([0 (2^k)*N, -2 2]);drawnow   yold= ynew;end;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%end;% TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%