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https://issues.apache.org/jira/browse/SPARK-5056?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14272458#comment-14272458
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Tomislav Milinovic commented on SPARK-5056:
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Partitioning Around Medoids (PAM) complexity of each iteration is O(k(n-k)2)
 For large values of n and k, such computation becomes very costly.

Clustering Large Applications (CLARA) is fully described in chapter 3 of 
Kaufman, L. and Rousseeuw, P.J. (1990) Finding Groups in Data: An Introduction 
to Cluster Analysis.Wiley, New York. 
Compared to other partitioning methods such as PAM, it can deal with much 
larger datasets. Internally, this is achieved by considering sub-datasets of 
fixed size (sampsize) such that the time and storage requirements become linear 
in n rather than quadratic.
CLARA complexity of each Iteration is: O(ks2 + k(n-k))
s: the size of the sample
k: number of clusters
n: number of objects


> Implementing Clara k-medoids clustering algorithm for large datasets
> --------------------------------------------------------------------
>
>                 Key: SPARK-5056
>                 URL: https://issues.apache.org/jira/browse/SPARK-5056
>             Project: Spark
>          Issue Type: Improvement
>          Components: MLlib
>            Reporter: Tomislav Milinovic
>            Priority: Minor
>              Labels: features
>
> There is a specific k-medoids clustering algorithm for large datasets. The 
> algorithm is called Clara in R, and is fully described in chapter 3 of 
> Finding Groups in Data: An Introduction to Cluster Analysis. by Kaufman, L 
> and Rousseeuw, PJ (1990). 
> The algorithm considers sub-datasets of fixed size (sampsize) such that the 
> time and storage requirements become linear in n rather than quadratic. Each 
> sub-dataset is partitioned into k clusters using the same algorithm as in 
> Partinioning around Medoids (PAM).



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