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In ecology, rarefaction is a technique to assess species richness from the results of sampling. Rarefaction allows the calculation of species richness for a given number of individual samples, based on the construction of so-called rarefaction curves. This curve is a plot of the number of species as a function of the number of samples.
Rarefaction is the reduction of an item's density, the opposite of compression. [1] Like compression, which can travel in waves ( sound waves , for instance), rarefaction waves also exist in nature. A common rarefaction wave is the area of low relative pressure following a shock wave (see picture).
The Cauchy distribution, an example of a distribution which does not have an expected value or a variance. In physics it is usually called a Lorentzian profile, and is associated with many processes, including resonance energy distribution, impact and natural spectral line broadening and quadratic stark line broadening.
This is a list of Wikipedia articles about curves used in different fields: mathematics (including geometry, statistics, and applied mathematics), ...
Relative species abundance of beetles sampled from the river Thames showing the universal "hollow curve". (derived from data presented in Magurran (2004) [2] and collected by C.B. Williams (1964) [3]) Relative species abundance and species richness describe key elements of biodiversity. [1]
Characteristics may fail to cover part of the domain of the PDE. This is called a rarefaction, and indicates the solution typically exists only in a weak, i.e. integral equation, sense. The direction of the characteristic lines indicates the flow of values through the solution, as the example above demonstrates.
The rarefaction curve, is defined as: = [] = () ... For example, five-, seven- and nine-point scales with a uniform distribution of responses give PCIs of 0.60, 0 ...
For electromagnetic waves in vacuum, the angular frequency is proportional to the wavenumber: =. This is a linear dispersion relation, in which case the waves are said to be non-dispersive. [1]