Hi,
While rewriting a script, I noticed that the sum of a vector changes if ifftshift/fftshift has been carried out. Take the following example:
t=-10:.1:10-.1; y=exp(-t.^2/2); s1=sum(y); s2=sum(ifftshift(y)); s3=sum(fftshift(y)); d1=vpa(s1-s2); d2=vpa(s1-s3);
I get the following: d1=d2=0.0000000000000035527136788005009293556213378906
I also found that I get the same difference if I carry out the shift manually like:
y2=[y(101:200),y(1:100)]; s4=sum(y2); s4-s2=0
So my question is, why does the sum of the vector change if the vector is shifted in this manner and are there any ways to make sure that the sum stays the same without having to evaluate both of the sums and then re-scaling the shifted vector?
Thanks in advance, Robert
