Dependency {NetIndices}

Direct and indirect dependency analysis

Description

Calculates for each component in a flow network the direct+indirect dependency on the other components.

Usage

Dependency(Flow = NULL, Tij = t(Flow), 
           Import = NULL, Export = NULL)

Arguments

Flow

network matrix with Flow[i,j] the flow from i (row) to j (column); component positions in rows and columns must be the same; if present, rownames or columnnames denote the compartment names.

Tij

network matrix where connectance is from column j to row i; component positions in rows and columns must be the same ; if present, rownames or columnnames denote the compartment names.

Import

vector with either the *indices* or the *names* of external compartmens from where flow enters the network; the indices point to the column positions in Tij (and the row positions in Flow).

Export

vector with either the *indices* or the *names* of external compartmens to where flow leaves the network; the indices point to the row positions in Tij (and the column positions in Flow).

Value

A matrix with dependency of component i on component j

Author(s)

Karline Soetaert <[e-mail]>, Julius Kipyegon Kones<[e-mail]>

References

Kones, J.K., Soetaert, K., van Oevelen, D. and J.Owino (2009). Are network indices robust indicators of food web functioning? a Monte Carlo approach. Ecological Modelling, 220, 370-382.

Examples

# The takapoto atoll network
Dependency(Takapoto, Import = "CO2",
           Export = c("CO2", "Sedimentation", "Grazing"))

# making "Bacteria" a "primary food source"  
TAK <- Takapoto
TAK[,"Bacteria"] <- c(0, 0, 0, 0, 0, 0, 1, 0)

# first two columns
DD <- Dependency(TAK, Import = c("CO2", "DOC"),
                 Export = c("CO2", "DOC", "Sedimentation", "Grazing"))
DD

barplot(t (DD[3:nrow(DD), 1:2]), beside = TRUE, ylab = "-",
       legend = c("Phytoplankton","Bacteria"),
       main = "dependency on (primary) food sources")