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. 2021 Feb 8;14(4):808. doi: 10.3390/ma14040808
Algorithm 1: Procedures used for grey relational analysis (GRA) [37,38,39,40,41,42,43].
  • 1
    Normalization: If the likelihood is the-smaller-the-netter (SB) or the-higher-the-better (HB),
    SB:xij(k)=maxxij(k)xij(k)maxxij(k)minxij(k)HB:xij(k)=xij(k)minxij(k)maxxij(k)minxij(k)
  • 2

    Evaluation of Δij : Δij=x0j(k)xij(k)

  • 3
    Grey relational coefficient calculation:
    γ(x0j,xij)=Δmin+ζΔmaxΔij(k)+ζΔmaxΔij=x0j(k)xij(k),
    where γ(x0j,xij) is the grey relational coefficient between xij and x0j. Δmax is the maximum value of Δij, and Δmin is the minimum value of Δij. ζ is the distinguishing coefficient (0ζ1), and assumed to be 0.5.
  • 4
    From the grey relational coefficient, the grey relational grade (GRG) is determined as follows:
    γi=1ni=1nγ(x0j,xij).
  • 5
    Considering the weighting method in real-time applications, the GRG can be rewritten as:
    γi=1ni=1nwkγ(x0j,xij),
    where wk is the weighting factor for k. In the present investigation, the weighting value wk for the response each parameter was estimated from the Shannon entropy weighting method.
  • 6

    Rank according to the values of the GRG in decreasing order.