File:Logistic curve vector field.png
Summary
| Description |
日本語: ロジスティック曲線とそのベクトル図。Scilabで作成 |
| Date | |
| Source | Own work |
| Author | Yapparina |
Scilab source
 |
This media was created with Scilab, a free open-source software. Here is a listing of the Scilab source used to create this file. |
clear
r=1; //intrinsic rate of natural increase
K=1; //carrying capacity
deff('[ydot]=g(t,y)',['ydot=r*y*(1-y/K)']);//logistic equation, y is population size, ydot is dy/dt
tc=-2:0.4:2;
nc=-1:0.2:2;
dx=zeros(length(tc),length(nc));
dy=zeros(length(tc),length(nc));
for nnc=1:length(nc)
for ntc=1:length(tc)
dx(ntc,nnc)=cos(atan(g(tc(ntc),nc(nnc))));
dy(ntc,nnc)=sin(atan(g(tc(ntc),nc(nnc))));
end
end
clf();
champ(tc, nc, dx, dy)
xtc=-2:0.01:2.2;
x=K./(1+(K./0.5-1)*exp(-r.*xtc));//logistic curve 1, the initial population size N0 = 0.5
plot2d(xtc,x)
xtc=-2:0.01:0.45;
x=K./(1+(K./-0.5-1)*exp(-r.*xtc));//logistic curve 2, N0 = -0.5
plot2d(xtc,x)
xtc=-0.4:0.01:2.2;
x=K./(1+(K./1.5-1)*exp(-r.*xtc));//logistic curve 3, N0 = 1.5
plot2d(xtc,x)
xlabel('t');
ylabel('N');
zoom_rect([-2.1,-1.3,2.3,2.1])
Licensing
I, the copyright holder of this work, hereby publish it under the following license:
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This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication. |
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