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Applied Unsupervised Learning with R

You're reading from   Applied Unsupervised Learning with R Uncover hidden relationships and patterns with k-means clustering, hierarchical clustering, and PCA

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Product type Paperback
Published in Mar 2019
Publisher
ISBN-13 9781789956399
Length 320 pages
Edition 1st Edition
Languages
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Authors (2):
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Bradford Tuckfield Bradford Tuckfield
Author Profile Icon Bradford Tuckfield
Bradford Tuckfield
Alok Malik Alok Malik
Author Profile Icon Alok Malik
Alok Malik
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Introduction to Kernel Density Estimation


So far, we've studied parametric distributions in this chapter, but in real life, all distributions are either approximations of parametric distributions or don't resemble any parametric distributions at all. In such cases, we use a technique called Kernel Density Estimation, or KDE, to estimate their probability distributions.

KDE is used to estimate the probability density function of distributions or random variables with given finite points of that distribution using something called a kernel. This will be more clear to you after you continue further in the chapter.

KDE Algorithm

Contrary to what it might seem like given the heavy name, KDE is a very simple two-step process:

  1. Choosing a kernel

  2. Placing the kernel on data points and taking the sum of kernels

A kernel is a non-negative symmetric function that is used to model distributions. For example, in KDE, a normal distribution function is the most commonly used kernel function. Kernel functions...

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