function alpha1=dfa_exponent(sig)
data=sig;
data=dtrend(data);
minbox=0;maxbox=0;
nfit=2;%set nfit (the order of the regression fit)
iflag=0;%input data are already integrated
sw=1;%enable sliding window mode
data=dtrend(data);
seq=[1;cumsum(data)];
%seq=[1;data];
npts=length(seq)-1;
% Set minimum and maximum box sizes
if (minbox< 2*nfit)
    minbox = 2*nfit;
end
if (maxbox == 0 || maxbox > npts/4) 
    maxbox = floor(npts/4);
end
if (minbox>maxbox) 
    temp = minbox; minbox = maxbox; maxbox = temp;
    if (minbox < 2*nfit) 
        minbox = 2*nfit;
    end
end
mex dfa_main.c
alpha1=dfa_main(seq,minbox,maxbox,npts,nfit);