dynamicVariation: Dynamic variation and variation decomposition

In ecotraj: Ecological Trajectory Analysis

Dynamic variation and variation decomposition

Description

• Function dynamicVariation assesses the amount of dynamic variation observed across trajectories and the relative contribution of each of them.

• Function variationDecomposition performs a sum of squares decomposition of total variation in three components: (1) across trajectories (entities); (2) across time points; (3) their interaction.

Usage

dynamicVariation(x, ...)

variationDecomposition(x)

Arguments

x	An object of class trajectories (or its children subclasses fd.trajectories or cycles).
...	Additional params to be passed to function trajectoryDistances.

Details

Function variationDecomposition requires trajectories to be synchronous. The SS sum of temporal and interaction components correspond to the SS sum, across trajectories, of function trajectoryInternalVariation.

Value

• Function dynamicVariance returns a list with three elements (dynamic sum of squares, dynamic variance and a vector of trajectory relative contributions)

• Function variationDecomposition returns a data frame with results (sum of squares, degrees of freedom and variance estimates) for each variance component and the total.

See Also

defineTrajectories, is.synchronous, trajectoryDistances, trajectoryInternalVariation

Examples

#Description of entities and surveys
entities <- c("1","1","1","1","2","2","2","2","3","3","3","3")
surveys <- c(1,2,3,4,1,2,3,4,1,2,3,4)
  
#Raw data table
xy<-matrix(0, nrow=12, ncol=2)
xy[2,2]<-1
xy[3,2]<-2
xy[4,2]<-3
xy[5:6,2] <- xy[1:2,2]
xy[7,2]<-1.5
xy[8,2]<-2.0
xy[5:6,1] <- 0.25
xy[7,1]<-0.5
xy[8,1]<-1.0
xy[9:10,1] <- xy[5:6,1]+0.25
xy[11,1] <- 1.0
xy[12,1] <-1.5
xy[9:10,2] <- xy[5:6,2]
xy[11:12,2]<-c(1.25,1.0)

d <- dist(xy)

# Defines trajectories
x <- defineTrajectories(d, entities, surveys)

# Assessment of dynamic variation and individual trajectory contributions
dynamicVariation(x)

# Variation decomposition (entity, temporal and interaction) for synchronous 
# trajectories:
variationDecomposition(x)

# check the correspondence with internal variation
sum(variationDecomposition(x)[c("time", "interaction"),"ss"])
sum(trajectoryInternalVariation(x)$internal_ss)

ecotraj documentation built on June 8, 2025, 11:24 a.m.