Xie-Beni fuzzy index for spherical clustering

Input: data set 𝒜 ⊂ (ℝ^n), centers (Subscript[c, 1]),⃛,(Subscript[c, k]) ∈ (ℝ^n), membership matrix U;
Output: FXB index;
Submodules: none needed

Clear[FXB]
FXB[A_,cen_,U_]:=Module[{m,k},m=Length[A];k=Length[cen];Sum[U[[i,j]]^q Norm[cen[[j]]-A[[i]]]^2,{i,m},{j,k}]/(m*Min[Flatten[Table[Norm[cen[[i]]-cen[[j]]]^2,{i,k-1},{j,i+1,k}],1]])
]