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PASCAL Bootcamp in Machine Learning
PASCAL

Lectures on Clustering

author: Ulrike von Luxburg, Max Planck Institute for Biological Cybernetics

Description

These lectures give an introduction to data clustering: we discuss a few algorithms, but also look at theoretical questions related to clustering. The first two lectures are devoted to spectral clustering: graph Laplacians and their properties, spectral clustering algorithms, mathematical derivations of the algorithms, and some implementation issues. Moreover, we discuss the related modularity approach for detecting communities in networks. The third lecture is devoted to the very general question "what clustering is". We try to look at clustering from different angles, discuss different definitions of clustering, and look into theoretical foundations of clustering in general. In the last lecture we work on the question how the number of clusters should be defined. The focus is on two popular approaches: the gap statistics and the stability approach.

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Slides
0:00 Clustering
0:41 Overview
1:46 Cliustering: Intuition
1:48 What is clustering, intuitively?
4:47 Example: Clustering gene expression data
5:57 Example: Social networks
6:52 Example: Image segmentation
7:16 Example: Genetic distances between mammals
8:15 Two classes of algorithms
8:17 The standard algorithm for "flat" clustering: K-means
8:30 Spectral clustering
8:46 Spectral clustering on one slide
10:50 Graph notation
14:36 Unnormalized graph Laplacian - 1
16:59 Graph notation
17:06 Unnormalized graph Laplacian - 1
18:01 Unnormalized graph Laplacian - 2
21:57 Unnormalized graph Laplacian - 3
26:02 Normalized graph Laplacians - 1
28:16 Normalized graph Laplacians - 2
28:17 Spectral clustering - main algorithms
33:32 Toy example with three clusters - 1
34:35 Toy example with three clusters - 2
35:50 Toy example with three clusters - 3
37:13 Toy example with three clusters - 4
42:47 Toy example with three clusters - 5
43:47 Toy example with three clusters - 6
43:49 Graph cut explanation of spectral clustering - 1
50:02 Graph cut explanation of spectral clustering - 2

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Part 1: Spectral clustering 0:58:33
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Part 2: Spectral clustering 0:51:05
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Part 3: What is clustering, after all? 0:51:00
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Part 4: Selecting the number of clusters 0:43:42
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Reviews and comments:

Comment1 Ryan, September 28, 2007 at 2:59 a.m.:

Please post these lectures in wmv format. Thanks


Comment2 naveen, February 22, 2008 at 11:45 a.m.:

The presentation is very good, but maybe the lectures could use a bit more detailed explanations for the benefit of less gifted students.


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