Home Forums PATN and Pattern Analysis PATN Discussion Comparing dendrograms

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  • #426
    rainman
    Member

    Hi all,

    I have generated two dendrograms that I would like to compare. They are based on the dietary composition of a range of fish species using: (a) broad prey categories, and (b) fine prey categories.

    While the species remain in the same groups at the finer level of resolution, the differences between groups are not as pronounced.

    I have posted the results here as a word document. The arrows represent the movement of two species between guilds from the dry season to the wet season.

    Can the values at the top of the two dendrograms be directly related to one another?

    Many thanks,
    Tom.

    #506
    lee
    Keymaster

    Hi Tom

    Depends on the data values and number of variables (an in this case, that would be different) and asuming same association measure, classification method/beta value).

    If you display the association matrix and look at the histograms of both datasets, you will see the ‘raw material’ for the classification. The similarity of the shapes, minimum and maximum values will be the determinants of dendrogram similarity.

    What many have done (self included) is to a) standardise the two association matrices 0-1 (say), and then b) subtract them to create a |absolute| difference matrix…then c) classify that!

    The last fusion values (an association value) in your case are 1.3165 and 1.3473 suggests (doesn’t prove) that the two association matrices were similarly structured, and does prove that space dilation was operating.

    Lee

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