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Running Start/CSB320 - Machine Learning Concepts/Class 5-28 (Clustering).md

@@ -6,4 +6,16 @@
 - clustering
 	- groups instances based on feature similarity
 	- results in group assignments, not target output
-	- 
+	- need to extrapolate meaning from clusters
+	- ![[ClusteringBasic.excalidraw]]
+	- applications
+		- taxonomy of living things
+		- clustering documents on topic
+		- identify areas with similar land use
+		- cluster groups of houses for city planning
+	- good clustering: high intra-class similarity, low inter-class similarity
+	- centroid
+		- mean position of a cluster's instances $$\overline X_{i}=\frac{\sum_{j \in C_{i}}X_{i}}{n_{i}}$$
+	- Inertia
+		- aerage squared distance of the instances from the centroid $$I_{i}=\frac{\sum_{j \in C_{i}}|\overline X_{j} - X_{i}|^2}{n_{i}}$$
+		-