"Importance of Z-transformation in clustering"

imfaithimfaith Member Posts: 14 Contributor II
edited June 13 in Help
Hello every body;

I haven't understand the importance of use Z-transformation in clustering process (for example k-means). It is necessary to use this transformation and what is its impact ? this transformation don't change the result of clustering ?  There are several methods of transformation, what is the most suitable for the clustering process ? ???
Thank you very much.
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Answers

  • wesselwessel Member Posts: 537  Guru
    Assuming you are using k-means uses squared distance.
    Assuming you create a a new attribute: att_1b = att_1 * 100.
    If you were to use att_1b instead of att_1 during clustering, distances in att1_b are far more importance, because of the scaling.
    Typically you want all attributes have equal weight in the distance calculation, Z-transforming all your attributes allows you to do just this.

    Best regards,

    Wessel
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