clear
n=4;
xd=(1:n);

//DCT Matrix
for i = 1:n,
    for j = 1:n, 
        if i==1 then c=1/sqrt(2); else c=1;end;
        a(i,j) = sqrt(2/n)*c*cos((i-1)*(j-1/2)*%pi/n);
    end;
end;
a;

//Input vector x

x=[1,0,0,0]',

//Filter

f=diag([ 0.8,0.4,0.2,0.1]),
//f=diag([ 1,1,1,1]), //In case of Non filter

//y=a*x; //t->f
//yy=f*y; //filtering
//xx=a'*yy; //f->t

W=a'*f*a,
xx=W*x,

xbasc();
bar(xx,0.5);

egval=spec(a'*f*a),