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# skbio.diversity.alpha.strong

`skbio.diversity.alpha.``strong`(counts)

  Calculate Strong’s dominance index.

  State: Experimental as of 0.4.0.

  Strong’s dominance index is defined as:

  \[D_w = max_i[(\frac{b_i}{N})-\frac{i}{S}]\]

  where \(b_i\) is the sequential cumulative totaling of the \(i^{\text{th}}\) OTU abundance values ranked from largest to smallest, \(N\) is the total number of individuals in the sample, and \(S\) is the number of OTUs in the sample. The expression in brackets is computed for all OTUs, and \(max_i\) denotes the maximum value in brackets for any OTU.

  Parameters: | counts (1-D array_like, int) – Vector of counts.
  Returns: | Strong’s dominance index (Dw).
  Return type: | double

  Notes

  Strong’s dominance index is defined in [1]. The implementation here is based on the description given in the SDR-IV online manual [2].

  References

  [1] | Strong, W. L., 2002 Assessing species abundance uneveness within and between plant communities. Community Ecology, 3, 237-246.

  [2] | http://www.pisces-conservation.com/sdrhelp/index.html