phaseArrows: phaseArrows

In pplane: Phase plane plots of 2D nonlinear systems

Description

plotting phase space vectors

Usage

phaseArrows(fDeriv, xlims = c(-3, 3), ylims = xlims, resol = 20, 


    isJitter = FALSE, add = F, arrowHeads = 0.04, arrowLength = 0.5, 


    col = rev(heat.colors(150))[-(1:50)], logLength = FALSE, 


    dimnames = NULL, ...)

Arguments

fDeriv	derivative function function(x,y,...)
xlims	numeric vector (2): range of the x values
ylims	numeric vector (2): range of the y values
resol	scalar integer: number of points in x and y range
isJitter	set to TRUE to jitter vector starting positions to avoid overplotting (however calculating contours does not work then anymore)
add	set to TRUE to add arrows to an existing plot
arrowHeads	size of the arrow heads (in inches), set t0 0 for heads, 0.04 gives nice results
arrowLength	length of the vectors, set to 0 to scale vectors with magnitude of flow
col	color scale
logLength	set to TRUE to calculate colors or length for log of the flow strength
dimnames	character vector(2): labels of the x and y axis, to overwrite defaults
...	further arguments to fun, such as parms

Value

result of evalDerivGrid: a list with entries

• z: numeric matrix vector (resol x resol,2): calculated flow at each of the grid (labels before before jittering)

• xy: numeric matrix (resol,resol,2): x and y values of the grid

Author(s)

Thomas Wutzler

Examples

fDeriv <- predatorprey(lambda=3, epsilon=2, delta=3, eta=2)


#


# set up a plotting window


# windows(width = 4.6, height = 3.2, pointsize = 10); par( las = 1, mar = c(2, 3.3, 0, 0) + 0.3, tck = 0.02, mgp = c(1.1, 0.2, 0))


#


# default: strength is colored, no arrow heads, same length


tmp <- phaseArrows( fDeriv, c(-2,5),c(-2,5) );


#phaseContours(tmp$z, tmp$xy, add=TRUE)


phaseNullclines(tmp$z, tmp$xy, add=TRUE)


drawTrajectories( fDeriv, tEnd=3, x0=list(x=1,y=2) )    # initial starting point by script


#drawTrajectories( fDeriv, tEnd=3, x0=locator(2,"p") )   # set the starting point in the graph: need to click several times


#


# add arrow heads and use colors for log scale, scale vector length


phaseArrows( fDeriv, c(-2,5),c(-2,5), logLength=TRUE, arrowHeads=0.04, arrowLength=0 );


#


# for background, sometimes a decent color is useful


tmp <- phaseArrows( fDeriv, c(-2,5),c(-2,5), col="grey" );


#


# may use parallel calculation of flow field and trajectories


if( FALSE ){    # do not run on R CMC check


    require(snowfall)


    tmp <- phaseArrows( fDeriv, c(-2,5),c(-2,5), useSnowfall=TRUE );       # using parallel calculation


    drawTrajectories( fDeriv, tEnd=3, x0=list(x=1,y=c(2:5)), fLapply=sfLapply )    # initial starting point by script


}

pplane documentation built on May 2, 2019, 6:07 p.m.