--- a
+++ b/testing/test_framemulappr.m
@@ -0,0 +1,50 @@
+
+% This test example is taken from demo_gabmulappr
+
+% Setup parameters for the Gabor system and length of the signal
+L=576; % Length of the signal
+a=32;   % Time shift 
+M=72;  % Number of modulations
+N=L/a;
+fs=44100; % assumed sampling rate
+SNRtv=63; % signal to noise ratio of change rate of time-variant system
+
+% construction of slowly time variant system
+% take an initial vector and multiply by random vector close to one
+A = [];
+c1=(1:L/2); c2=(L/2:-1:1); c=[c1 c2].^(-1); % weight of decay x^(-1)
+A(1,:)=(rand(1,L)-0.5).*c;  % convolution kernel
+Nlvl = exp(-SNRtv/10);
+Slvl = 1-Nlvl;
+for ii=2:L;
+     A(ii,:)=(Slvl*circshift(A(ii-1,:),[0 1]))+(Nlvl*(rand(1,L)-0.5)); 
+end;
+A = A/norm(A)*0.99; % normalize matrix
+
+% perform best approximation by gabor multiplier
+g=gabtight(a,M,L);
+sym1=gabmulappr(A,g,a,M);
+
+
+% Now do the same using the general frame algorithm.
+
+F=frame('dgt',g,a,M);
+
+sym2=framemulappr(F,F,A);
+
+
+norm(sym1-reshape(sym2,M,N))
+
+% Test for exactness
+
+testsym=crand(M,N);
+FT=framematrix(F,L);
+
+T=FT*diag(testsym(:))*FT';
+
+
+sym1b=gabmulappr(T,g,a,M);
+sym2b=framemulappr(F,F,T);
+
+norm(testsym-sym1b)
+norm(testsym-reshape(sym2b,M,N))