Random Link ¯\_(ツ)_/¯ Oct 10, 2020 » Similarity Measures 2 min; updated Mar 14, 2021 To classify something, find things that are similar and label it with the same class as the most similar thing. The feature space is $$N-d$$, where $$N$$ is the number of features. Each instance is mapped to a point. The descriptive features become the axes. The Similarity Metric Mathematically, it must conform to these 4 criteria: Non-negative: $$f(a, b) \ge 0$$ Identity: $$f(a, b) = 0 \iff a = b$$ Symmetry: $$f(a, b) = f(b, a)$$ Triangular inequality: $$f(a, b) \le f(a, c) + f(c, b)$$ Why are non-negativity and triangular inequality important?... Oct 10, 2020 » Similarity Measures 2 min; updated Mar 14, 2021 To classify something, find things that are similar and label it with the same class as the most similar thing. The feature space is $$N-d$$, where $$N$$ is the number of features. Each instance is mapped to a point. The descriptive features become the axes. The Similarity Metric Mathematically, it must conform to these 4 criteria: Non-negative: $$f(a, b) \ge 0$$ Identity: $$f(a, b) = 0 \iff a = b$$ Symmetry: $$f(a, b) = f(b, a)$$ Triangular inequality: $$f(a, b) \le f(a, c) + f(c, b)$$ Why are non-negativity and triangular inequality important?...