From 7c5034bcbc4078816bbb3200886b389f97a154d2 Mon Sep 17 00:00:00 2001
From: "Velimir V Vesselinov (monty)" <velimir.vesselinov@gmail.com>
Date: Mon, 9 Jul 2018 17:51:45 -0600
Subject: [PATCH] 0 silhouette score set for clusers of size 1 (#120)

---
 src/silhouette.jl  | 16 ++++++++++------
 test/silhouette.jl |  5 +++++
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/silhouette.jl b/src/silhouette.jl
index 2b2c8ea4..70dd64c1 100644
--- 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
index e86d6c36..71c7930f 100644
--- 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]))
\ No newline at end of file