I'm just getting started with learning about K-nearest neighbor and am having a hard time understanding why standardization is required. Reading through, I came across a section saying

When independent variables in training data are measured in different units, it is important to standardize variables before calculating distance. For example, if one variable is based on height in cms, and the other is based on weight in kgs then height will influence more on the distance calculation.

Since K nearest neighbor is just a comparison of distances apart, why does it matter if one of the variables has values of a larger range since it is what it is.

Also,what exactly does standardization do to the values? One of the formulas does it by Xs = (X-mean)/(max-min) Where does such a formula come from and what is it really doing? Hopefully someone can offer me a simplified explanation or give me a link to a site or book that explains this in simple terms for beginners.

  • $\begingroup$ If you are citing text from a book, lecture notes, article, or whatever, then please add a reference so proper credit is given to the author. $\endgroup$
    – dkaeae
    Aug 21 '19 at 13:04

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