ShanKothari / DecomposingFD

Code to calculate functional trait diversity as defined by Scheiner et al. (2016), and its decomposition into richness, evenness, and dispersion.
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Non-additivity across scales #4

Open ShanKothari opened 6 years ago

ShanKothari commented 6 years ago

Various metrics are not completely multiplicative, even though they are claimed to be. For example, mean alpha dispersion (0.3088132) and beta dispersion (0.1650757) do not sum to gamma dispersion (0.4725226) with the following data set (q=1, no abundances).

FABdata.zip

The issue is not likely to be related to whether or not one should always use the arithmetic mean (vs. a generalized mean dependent on p=1-q) to calculate Sw, M, and analogous components, because it should still be additive either way, in case q=0.