dushoff.github.io/steps.R at master · dushoff/dushoff.github.io · GitHub

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par (cex=1.5)

finTime <- 8
i0 <- 10
C <- 4

steps <- 2
mult <- 6
ss <- mult*steps

basePlot <- function(t, i){
	plot(t, i
		, type = "l"
		, xlab = "Time (weeks)"
		, ylab = "Weekly incidence"
	)
}

arrowStep <- function(t, i, astart, adist, asteps, ss){
	pts <- (astart + adist*(0:asteps)/asteps)*ss
	x <- t[pts]
	y <- i[pts]
	points(c(min(x), max(x)), c(min(y), max(y)))
	arrows(x[-length(x)], y[-length(y)]
		, x[-1], y[-length(y)]
	)
	arrows(x[-1], y[-length(y)]
		, x[-1], y[-1]
		, length=0
	)
}

t <- (0:(finTime*ss))/ss
i <- i0*exp(t/C)

basePlot(t, i)
arrowStep(t, i, astart=3, adist=4, asteps=3, ss)

basePlot(t, i)
arrowStep(t, i, astart=3, adist=4, asteps=2, ss)