我的任务是创建一个程序,使用公式x_new = r * x_previous * (1-x_previous)
模拟人口增长,其中r
是生育力参数,x
是人口。我有一个工作程序和方法。但是,我的数学不是退房。我应该能够测试.01
的初始种群,1.1
的生育力参数,1000
时间步长并得到围绕.09
的答案)。
这是我的计划:
import java.util.Scanner;
public class Lab6Question3 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("The population, p: ");
double p = input.nextDouble();
System.out.println("The fecundity rate, r: ");
double r = input.nextDouble();
System.out.println("Number of Time Steps, n: ");
int n = input.nextInt();
int i; //iterations
System.out.println("-------------------------------------");
System.out.println("Simulation with starting population " + p);
System.out.println("Running " + n + " steps");
System.out.println("Varying fecundicity 1, 1.1, ..., 4.9, 5");
for (i = 0; i < n; i++) {
System.out.println("r = " + r + " final population = " + p);
r = r + 0.1;
p = populationGrowth(p, r);
}
}
public static double populationGrowth(double population, double fecundicity)
{
double p;
return (fecundicity * population * (1 - population));
}
}
并且我的输出使用迭代正确格式化,但是人口结果是错误的:
Simulation with starting population 0.01
Running 10000 steps
Varying fecundicity 1, 1.1, ..., 4.9, 5
r = 1.0 final population = 0.01
r = 1.1 final population = 0.01089
r = 1.2000000000000002 final population = 0.012925689480000004
r = 1.3000000000000003 final population = 0.01658620084090661
.
.
.
什么想法可能是疼痛的原因?提前致谢!
当r
达到5.2
关于迭代43
你的增长函数变为负数,因为x_previous is > 1
...所以1-x_previous < 0
,你确定模型是正确的......它似乎是一个概念问题。尝试在excel中对其进行建模。
另一件事,你在计算下一个r
值之前增加你p
。你确定是吗?