Bray Curtis dissimilarity

In ecology and biology, the Bray–Curtis dissimilarity, named after J. Roger Bray and John T. Curtis, is a statistic used to quantify the compositional dissimilarity between two different sites, based on counts at each site. As defined by Bray and Curtis, the index of dissimilarity is:

Where ${\displaystyle C_{ij}}$ is the sum of the lesser values for only those species in common between both sites. ${\displaystyle S_{i}}$ and ${\displaystyle S_{j}}$ are the total number of specimens counted at both sites. The index reduces to 1-2C/2 = 1-C where abundances at each site are expressed as a percentage. Further treatment can be found in Legendre & Legendre

The Bray–Curtis dissimilarity is directly related to the Sørensen similarity index ${\displaystyle QS_{ij}}$ between the same sites:

...
Wikipedia