0.5455
54.55
%
0.4545
0.5455
54.55
%
0.4545
The Sorensen Similarity Index Calculator (also known as the Dice coefficient) quantifies the similarity between two ecological communities based on shared species. Like the Jaccard Index, it ranges from 0 (no shared species) to 1 (identical composition), but it gives more weight to shared species, making it a more commonly preferred metric in ecological studies.
The Sorensen Index is especially popular in vegetation ecology, wildlife surveys, and biogeography for comparing species lists between habitats, seasons, or geographic areas.
The Sorensen Similarity Index is calculated as:
S = 2C / (A + B)
Where:
Doubling C in the numerator gives shared species extra weight compared to the Jaccard Index. The Sorensen Distance (1 - S) is used as a dissimilarity measure in multivariate community analysis.
Inputs
Results
S = 2(15) / (25+30) = 30/55 = 0.545. The Sorensen value is higher than the Jaccard value (0.375) for the same data.
Inputs
Results
S = 78/82 = 0.951, indicating nearly identical species composition between the two communities.
The Sorensen Index doubles the shared species count in the numerator (2C / (A+B)) while the Jaccard Index uses C / (A+B-C). This means Sorensen gives more weight to species the communities have in common, producing higher similarity values for the same data.
Yes. The Sorensen-Dice coefficient, Dice similarity coefficient, and Sorensen Similarity Index all refer to the same formula: 2C / (A + B). It was independently proposed by botanist Thorvald Sorensen (1948) and mathematician Lee Raymond Dice (1945).
The basic Sorensen Index requires presence-absence data: species lists for each community. You need the total species count in each community and the count of species found in both. It does not account for species abundances; for that, use the quantitative Sorensen or Bray-Curtis dissimilarity.
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