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How is the Hellinger transformation used in data matrix?
Like the Hellinger transformation, this transformation gives low weights to variables with low counts and many zeros. This transformation divides each value in a data matrix by the square root of its marginal sum of squares. It thereby sets the marginal (either row or column) sum of squares to one.
How are Hellinger transformed data used in ordination?
(b) Hellinger transformed data could be used in ordination methods using Euclidean distance (e.g. PCA, RDA, K-means clustering), in which case these methods use Hellinger distances (Hellinger transformed data + Euclidean distance = Hellinger distance). From Legendre & Legendre (2012), modified from Legendre & Gallagher (2001).
How is Hellinger distance calculated from species composition data?
Figure 3: (a) Hellinger distance can be calculated either directly from raw species composition data, or by first transforming species composition data by Hellinger transformation (standardization) and then applying Euclidean distance on these transformed data.
Which is better Euclidean distance or Hellinger distance?
The Euclidean distance (implicit for PCA/RDA ( Fig. 3) when applied on Hellinger-transformed species composition data results in Hellinger distance, which is more suitable for ecological data because (contrary to Euclidean distance) it is asymmetrical (ignores double zeros).
Is the Hellinger transformation square root of relative abundance?
It is my understanding that the Hellinger transformation is basically the square root of relative abundance data (if rows are samples). However, my row sums do not represent the total community (I am only looking at a fraction of it), and I am interested in keeping it that way.
When to use the Hellinger transformation in ecology?
If you have a large number of taxa, in my experience I have found applying the Hellinger transformation (or just the square root to already proportional abundance data) to be an improvement over and above just analysing the % (or proportional) abundance data. Thanks for contributing an answer to Cross Validated!
Which is the Hellinger transform for phyloseq objects?
In transformation typ, the ‘compositional’ abundances are returned as relative abundances in [0, 1] (convert to percentages by multiplying with a factor of 100). The Hellinger transform is square root of the relative abundance but instead given at the scale [0,1]. The log10p transformation refers to log10 (1 + x).