cheddar (version 0.1-639)

Degree: Node degree

Description

The number of trophic links in to and out of nodes in a Community.

Usage

Degree(community)
InDegree(community)
TrophicGenerality(community)
NumberOfResources(community)
OutDegree(community)
TrophicVulnerability(community)
NumberOfConsumers(community)
NormalisedTrophicGenerality(community)
NormalisedTrophicVulnerability(community)

Value

A vector of length NumberOfNodes.

Arguments

community

an object of class Community.

Author

Lawrence Hudson

Details

InDegree and OutDegree return the number of trophic links in-to and out-of each node. Degree returns InDegree + OutDegree. TrophicGenerality and NumberOfResources are synonyms for InDegree. TrophicVulnerability and NumberOfResources are synonyms for OutDegree.

NormalisedTrophicGenerality and NormalisedTrophicVulnerability return the containing the number of resources and consumer of each node, normalised with respect to LinkageDensity. The mean of the values returned by both NormalisedTrophicGenerality and NormalisedTrophicVulnerability is 1, making their standard deviations comparable across different food webs.

References

Williams, R.J. and Martinez, N.D. (2000) Simple rules yield complex food webs. Nature 404, 180--183.

See Also

Community, NumberOfNodes, LinkageDensity, DirectedConnectance, DegreeDistribution

Examples

data(TL84)

d <- Degree(TL84)
i <- InDegree(TL84)
o <- OutDegree(TL84)

# This equality is always TRUE for all food webs
all(d == i+o)

ntg <- NormalisedTrophicGenerality(TL84)
mean(ntg)    # Equals 1
ntv <- NormalisedTrophicVulnerability(TL84)
mean(ntv)    # Equals 1