Variance and covariances in multiscale

I want to code for DFA and DCCA based regression, to do i would like to code a detrended scale covariance and variance, as described in equation 4 and 5 in the following paper:

 https://arxiv.org/pdf/1411.0496.pdf

The beta coefficient is in eq 6 in the same paper.

When comparing my results to those found by the author in another paper when he made estimation, i have some differences. May be something wrong in my code.

inclosed the codes used to compute DFA and DCCA

if true
  % code
end