Similarity and dissimilarit Similarity/dissimilarity between objects is often expressed in terms of a distance measure d(x, y) a Ideally, every distance measure should be a metric. i.e. it should satisfy the following conditions (x,y)≥0 2. d(x,y)=oiff x 3.d(x,y)=d(y,x) 4.d(x,2)≤d(x,y)+d(y,2)Similarity and dissimilarity 9 ◼ Similarity/dissimilarity between objects is often expressed in terms of a distance measure d(x,y) ◼ Ideally, every distance measure should be a metric, i.e., it should satisfy the following conditions: 4. ( , ) ( , ) ( , ) 3. ( , ) ( , ) 2. ( , ) 0 iff 1. ( , ) 0 d x z d x y d y z d x y d y x d x y x y d x y  + = = = 