[R] Error in eco-model

[roelvhoolst]

Hello,

I am working on a paper of ecological modelling in R. I have made a Lotka
Volterra model for tree animal species. I was trying to get the model in R
but there are some errors. Since i am not so experienced with R i can't find
the bugs in my script.
I hope if there is someone who can help me handle this problem.

Greetz 

Roel

This is the script i wrote:

library(odesolve)

LotVmod <- function (Time, State, Pars) {
	with(as.list(c(State, Pars)), {
		dx = x*(alpha - beta*y)
		dy = -y*(gamma - delta*z)
		dz = z*( Iota – kappa*y)
		return(list(c(dx, dy, dz)))
	})
}

Pars <- c(alpha = .405, beta = .81, gamma = 1.5, delta = .125, Iota = 0.35,
kappa = 0.75)
State <- c(x = 100, y = 100, z = 100)
Time <- seq(0, 100, by = 1)

out <- as.data.frame(lsoda(func = LotVmod, y = State, parms = Pars, times =
Time))

matplot(out[,-1], type = "l", xlab = "time", ylab = "population")
legend("topright", c("leeuw", "wildebeest",”zebra”), lty = c(1,2,3), col =
c(1,2,3), box.lwd = 0)

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