rinter: Generate interaction point patterns

In stpp: Space-Time Point Pattern Simulation, Visualisation and Analysis

Generate interaction point patterns

Description

Generate one (or several) realisation(s) of the inhibition or contagious process in a region S\times T.

Usage

 rinter(npoints,s.region,t.region,hs="step",gs="min",thetas=0,
 deltas,ht="step",gt="min",thetat=1,deltat,recent="all",nsim=1,
 discrete.time=FALSE,replace=FALSE,inhibition=TRUE,...)

Arguments

npoints	Number of points to simulate.
s.region	Two-column matrix specifying polygonal region containing all data locations. If s.region is missing, the unit square is considered.
t.region	Vector containing the minimum and maximum values of the time interval. If t.region is missing, the interval [0,1] is considered.
hs, ht	Function which depends on the distance between points and theta. Can be chosen among "step" and "gaussian" or can refer to a user defined function which only depend on d, theta, and delta (see details). If inhibition=TRUE, h is monotone, increasing, and must tend to 1 when the distance tends to infinity. 0 \leqh(d,theta)\leq 1. Otherwise, h is monotone, decreasing, and must tend to 1 when the distance tends to 0.
thetas, thetat	Parameters of hs and ht functions.
deltas, deltat	Spatial and temporal distance of inhibition.
gs, gt	Compute the probability of acceptance of a new point from hs or ht and recent. Must be choosen among "min", "max" and "prod".
recent	If “all” consider all previous events. If is an integer, say N, consider only the N most recent events.
nsim	Number of simulations to generate. Default is 1.
discrete.time	If TRUE, times belong to N, otherwise belong to {\bf R}^+.
replace	Logical. If TRUE allows times repeat.
inhibition	Logical. If TRUE, an inhibition process is generated. Otherwise, it is a contagious process.
...	Additional parameters if hs and ht are defined by the user.

Value

A list containing:

xyt	Matrix (or list of matrices if nsim>1) containing the points (x,y,t) of the simulated point pattern. xyt (or any element of the list if nsim>1) is an object of the class stpp.
s.region, t.region	Parameters passed in argument.

Author(s)

Edith Gabriel <[e-mail]>, Peter J Diggle.

See Also

plot.stpp, animation and stan for plotting space-time point patterns.

Examples

# simple inhibition process
inh1 = rinter(npoints=200,thetas=0,deltas=0.05,thetat=0,deltat=0.001,
inhibition=TRUE)
plot(inh1$xyt,style="elegant")


# inhibition process using hs and ht defined by the user
hs = function(d,theta,delta,mus=0.1)
{
 res=NULL
 a=(1-theta)/mus
 b=theta-a*delta
 for(i in 1:length(d))
	{	
	if (d[i]<=delta) res=c(res,theta)
	if (d[i]>(delta+mus)) res=c(res,1)
	if (d[i]>delta & d[i]<=(delta+mus)) res=c(res,a*d[i]+b)
	}
 return(res)
}
ht = function(d,theta,delta,mut=0.3)
{
 res=NULL
 a=(1-theta)/mut
 b=theta-a*delta
 for(i in 1:length(d))
	{	
	if (d[i]<=delta) res=c(res,theta)
	if (d[i]>(delta+mut)) res=c(res,1)
	if (d[i]>delta & d[i]<=(delta+mut)) res=c(res,a*d[i]+b)
	}
 return(res)
}
d=seq(0,1,length=100)
plot(d,hs(d,theta=0.2,delta=0.1,mus=0.1),xlab="",ylab="",type="l",
ylim=c(0,1),lwd=2,las=1)
lines(d,ht(d,theta=0.1,delta=0.05,mut=0.3),col=2,lwd=2)
legend("bottomright",col=1:2,lty=1,lwd=2,legend=c(expression(h[s]),
expression(h[t])),bty="n",cex=2)

inh2 = rinter(npoints=100, hs=hs, gs="min", thetas=0.2, deltas=0.1, 
ht=ht, gt="min", thetat=0.1, deltat=0.05, inhibition=TRUE)
animation(inh2$xyt, runtime=15, cex=0.8)

# simple contagious process for given spatial and temporal regions
data(northcumbria)
cont1 = rinter(npoints=100, s.region=northcumbria, t.region=c(1,200), 
thetas=0, deltas=10000, thetat=0, deltat=10, recent=1, inhibition=FALSE)
plot(cont1$xyt,pch=19,s.region=cont1$s.region,mark=TRUE,mark.col=4)

stpp documentation built on June 28, 2024, 9:11 a.m.