practice 6.2 pretest.Rmd

---
title: "practice 6.2 pretest"
output:
  html_document: default
  word_document: default
date: "2022-10-28"
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)

```

```{r, eval=F, include=T}
grow<-function(start_1, start_2){
  num_gen<-30
  N1 <- rep(0,num_gen)
  N2 <- rep(0,num_gen)
  generation<-1:num_gen
  growth.rate<-1.2
  K1<-100
  K2<-120
  a12<-0.8
  a21<-0.8
  N1[1]<-start_1
  N2[1]<-start_2
  for (i in 2:num_gen)  {
    N1[i] = N1[i-1] + (3.2* N1[i-1] * ((K1-N1[i-1]-(a12*N2[i-1]))/K1))
    N2[i] = N2[i] + (growth.rate * N2[i-1] * ((K2-N2[i-1]-(a21*N1[i-1]))*K2))
    #generation[1]=1 
   print (N1[i])
  }
  if (N1[1]>2){
    plot(N1~generation,typ="b",ylim=c(0,min(c(K1,K2))),ylab="N")
  }  else {
    plot(N1~generation,typ="n",ylim=c(0,min(c(K1,K2))),ylab="N")
  }
  print(N2[1])
  if (N2[1]>0){
    lines(N2~generation,typ="b",col=2)}
}
grow(1,0)；
grow(1,2)
par(mar=c(9,4,1,1),mfrow=c(5,1),las=1)

grow(1,0)
text(4,110,"Species 1 alone")

grow(0,1)
text(4,110,"Species 2 alone")

grow(1,2)
text(6,110,"Both Species competing")
```