accf=fft([zeros(1000,3);acc;zeros(1000,3)]);
cutoff1=0;
X1=[0,0,0;
zeros(round((size(accf,1)-1)/2*cutoff1/50),3); %% 50 ??
ones(ceil((size(accf,1)-1)/2)-round((size(accf,1)-1)/2*cutoff1/50),3);
ones(floor((size(accf,1)-1)/2)-round((size(accf,1)-1)/2*cutoff1/50),3);
zeros(round((size(accf,1)-1)/2*cutoff1/50),3)];
X2=angle(accf);
X=X1.*exp(X2*sqrt(-1));
acc=real(ifft(X));
acc=acc(1001:end-1000,:);
I guess this is some kind of filtering. Can you help me to find the reference materials for the math?