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. 2022 May 7;22(9):3557. doi: 10.3390/s22093557
Algorithm 1: Spectral clustering process with a metric ρ.
  • Input: (data) {xi}i=1n, (kernel function) fσ, and (scaling parameter) σ>0

  • Output: Y(labels) with clustered values
    •  1. The weight matrix W∈ℜn×n is computed with Wij=fσ(ρ(xi,xj)).
    •  2. The diagonal degree matrix D∈ℜn×n is computed with Dii=∑j=1nWij.
    •  3. The symmetric normalized Laplacian LSYM=I−D−12WD−12 is formed.
    •  4. The eigendecomposition {(ϕk,λk)}k=1n is computed and sorted so that 0=λ1≤λ2≤…≤λn.
    •  5. The number of clusters K is estimated as: K^=argmaxkλk+1−λk.
    •  6. The row normalized spectral embedding is defined by vi=(ϕ1(xi),ϕ2(xi),…,ϕk^(xi))/‖ϕ1(xi),ϕ2(xi),…,ϕk^(xi)‖2 for 1≤i≤n.
    •  7. By implementing K-means on the data {vi}i=1n, the labels Y are computed by utilizing K^ as the total number of clusters, thereby implementing the concept of clustering successfully.