NtPlus1<-Nt*exp(r*(1-Nt))
return(NtPlus1) #  you can omit ‘return’ and just write NtPlus1
}
minimum_r <-0.001 # set the starting value of r
maximum_r <-5
r_sequence <- seq(minimum_r,maximum_r,0.001) 
plot(NULL,xlim=range(r_sequence),ylim=c(0,5), xlab="r",ylab="Nt",main="Ricker logistic population model") # create a blank plotting field
for (r in r_sequence){  
 	Nt <- runif(1) 
	for (i in 1:200) Nt <- ricker(Nt,r) 
	for (i in 1:200){Nt <- ricker(Nt,r) 
		points(r,Nt,pch=".",cex=1.5)} 
}