0 silhouette score set for clusers of size 1 (#120)

JuliaStats · Jul 9, 2018 · 7c5034b · 7c5034b
1 parent d076fd8
commit 7c5034b
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Showing 2 changed files with 15 additions and 6 deletions.
diff --git a/src/silhouette.jl b/src/silhouette.jl
@@ -22,8 +22,8 @@ function sil_aggregate_dists(k::Int, a::AbstractVector{Int}, dists::DenseMatrix{
 end
 
 
-function silhouettes(assignments::Vector{Int}, 
-                     counts::AbstractVector{Int}, 
+function silhouettes(assignments::Vector{Int},
+                     counts::AbstractVector{Int},
                      dists::DenseMatrix{T}) where T<:Real
 
     n = length(assignments)
@@ -69,13 +69,17 @@ function silhouettes(assignments::Vector{Int},
         b[j] = v
     end
 
-    # compute silhouette score 
+    # compute silhouette score
     sil = a   # reuse the memory of a for sil
     for j = 1:n
-        @inbounds sil[j] = (b[j] - a[j]) / max(a[j], b[j])
+        if counts[assignments[j]] == 1
+            sil[j] = 0
+        else
+            @inbounds sil[j] = (b[j] - a[j]) / max(a[j], b[j])
+        end
     end
     return sil
 end
 
-silhouettes(R::ClusteringResult, dists::DenseMatrix) = 
-    silhouettes(assignments(R), counts(R), dists) 
+silhouettes(R::ClusteringResult, dists::DenseMatrix) =
+    silhouettes(assignments(R), counts(R), dists)
diff --git a/test/silhouette.jl b/test/silhouette.jl
@@ -17,3 +17,8 @@ a = [1, 2, 1, 2]
 c = [2, 2]
 
 @test all(isapprox.(silhouettes(a, c, D), [0.0, -0.5, -0.5, 0.0]))
+
+a = [1, 1, 1, 2]
+c = [3, 1]
+
+@test all(isapprox.(silhouettes(a, c, D), [0.5, 0.5, -1/3, 0.0]))