OCNet (version 0.4.0)

continue_OCN: Perform OCN Search Algorithm on an Existing OCN

Description

Function that performs the OCN search algorithm on an existing OCN.

Usage

continue_OCN(OCN,nNewIter, coolingRate=NULL, initialNoCoolingPhase=0,
 displayUpdates=1, showIntermediatePlots=FALSE, thrADraw=NULL,
 easyDraw=NULL, nUpdates=50)

Arguments

OCN

Optimal Channel Network (as generated by create_OCN).

nNewIter

Number of iterations that the OCN search algorithm performs.

coolingRate

Parameter of the function used to describe the temperature of the simulated annealing algorithm. See create_OCN. If NULL, it is set equal to the last element of OCN$coolingRate.

initialNoCoolingPhase

Parameter of the function used to describe the temperature of the simulated annealing algorithm. See create_OCN.

nUpdates

Number of updates given during the OCN search process (only effective if any(displayUpdates,showIntermediatePlots)=TRUE.).

showIntermediatePlots

If TRUE, the OCN plot is updated nUpdates times during the OCN search process. Note that, for large lattices, showIntermediatePlots = TRUE might slow down the search process considerably (especially when easyDraw = FALSE).

thrADraw

Threshold drainage area value used to display the network (only effective when showIntermediatePlots = TRUE).

easyDraw

Logical. If TRUE, the whole network is displayed (when showIntermediatePlots = TRUE), and pixels with drainage area lower than thrADraw are displayed in light gray. If FALSE, only pixels with drainage area greater or equal to thrADraw are displayed. Default is FALSE if dimX*dimY <= 40000, and TRUE otherwise. Note that setting easyDraw = FALSE for large networks might slow down the process considerably.

displayUpdates

State if updates are printed on the console while the OCN search algorithm runs.

0

No update is given.

1

An estimate of duration is given (only if dimX*dimY > 1000, otherwise no update is given).

2

Progress updates are given. The number of these is controlled by nUpdates

Value

A list analogous to the input OCN. Note that, unlike in create_OCN, OCN$coolingRate and OCN$initialNoCoolingPhase are now vectors (of length equal to the number of times continue_OCN has been performed on the same OCN, plus one) that store the full sequence of coolingRate, initialNoCoolingPhase used to generate the OCN. Additionally, the vector OCN$nIterSequence is provided, with entries equal to the number of iterations performed by each successive application of create_OCN or continue_OCN. It is OCN$nIter = sum(OCN$nIterSequence).

Examples

# NOT RUN {
set.seed(1)
OCN_a <- create_OCN(20, 20, nIter = 16000)
set.seed(1)
OCN_b <- create_OCN(20, 20, nIter = 8000)
OCN_b <- continue_OCN(OCN_b, nNewIter = 8000)

old.par <- par(no.readonly = TRUE)
par(mfrow=c(1,2))
draw_simple_OCN(OCN_a)
draw_simple_OCN(OCN_b) # the two OCNs are equal
par(old.par)
# }