gap breaks on first local maxima

GapSpectral.m

@@ -52,6 +52,11 @@
 
 function [kGap Gap S idx] = GapSpectral(DistanceMatrix,nMaxClusters,bAlgorithmicInformationDistance)
 
+kGap=-1;
+Gap=[];
+S=[];
+idx=[];
+
 if nargin<3
     bAlgorithmicInformationDistance=1;
 end
@@ -99,17 +104,25 @@ for k=1:nMaxClusters
     S(k)=sdk * sqrt(1+1/B);
     %     Gap
     %     S
+    if k>1
+        if Gap(k-1)>=Gap(k)-S(k)
+            % found it!
+            kGap=k-1;
+            break;
+        end
+    end
 end
 
-figure
-errorbar( [1:nMaxClusters],Gap,S)
-set(gca,'XTick',[1:nMaxClusters])
-
-k=1;
-while ((k<nMaxClusters) && (Gap(k) < Gap(k+1)-S(k+1)))
-    k=k+1;
+if kGap<0
+    % rut roh!
+    fprintf(2,'error - gap did not converge?\n')
 end
-kGap=k;
+
+% 
+% figure
+% errorbar( [1:length(Gap)],Gap,S)
+% set(gca,'XTick',[1:length(Gap)])
+
 if (kGap>1)
     idx = SpectralCluster(D,kGap);
 else