Question

我将Lotka Voterra模型（猎物 - 食肉动物）作为Scilab函数编写并用ODE解决了它。我的问题是我想看到流量的演变。我通过在分辨率中包含流程找到了一个解决方案（在下面的脚本中只有一个），但它真的“很重”。任何人都有更好的解决方案吗？

//parameters
x=[0.04,0.005,0.3,0.2]
n = x(1);//birth rate of prey
c = x(2);//capture rate
e = x(3);//energy from capture
m = x(4);//death rate or predator

Tmax=100; // maximum time of simulation 
dt=0.01; // step of time 
t=0:dt:Tmax; //simulation time definition 
Ci = [20,30,0]'; //initial conditions (including for 1 flow)

//Lotka Volterra model
function [dy]=LV(t, y, n, c, e, m)
    GrowthP = n * y(1)
    IngestC = c * y(1) * y(2)
    MortC = m * y(2)
    dy(1) = GrowthP - IngestC
    dy(2) = IngestC * e - MortC
    dy(3) = IngestC //here one flow in ode
endfunction 

//resolution
sol=ode(Ci,0,t,LV)

//dataframe creation to stock data
soldef=zeros(3,10001);

//for the line 3 and form 2 to the last data it take the value, 
//remove the one of the previous time step and store it in soldef
for i = 2:length(sol(3,:))
    soldef(3,i)=sol(3,i)-sol(3,i-1);
end

//complete the dataframe with the stock
soldef(1:2,:)=sol(1:2,:)

感谢您对我的问题感兴趣和时间（对不起我的英语）

Answer 1

如果您想要对结果进行动画显示，可以使用下面的代码在图表上绘制越来越多的数据：

[row,col]=size(soldef);
scf(0);
clf(0);
plot2d(soldef(:,1:2)',rect=[0,0,col,max(soldef)]);  //plot first 2 points
en=gce();   //handle of the graphic entities
for i=3:col   //plot more and more points
  en.children(1).data=[1:i;soldef(3,1:i)]';   //update data matrices
  en.children(2).data=[1:i;soldef(2,1:i)]';
  en.children(3).data=[1:i;soldef(1,1:i)]';
  //you can save the frames here...
  xpause(1e4);    //wait some time if amination is too fast
end

如果您保存所有图表（例如xs2gif()），使用外部应用程序（google for“gif maker”），您甚至可以将结果的.gif动画嵌入到网页或演示文稿中。

在Scilab函数中求解模型时如何查看/提取模型流演变？

1 个答案: