to setup
  clear-all
  system-dynamics-setup
  
end

to go
  system-dynamics-go
  system-dynamics-do-plot
end

• a 羊的净出生率

a
0.001

sheep_birth
a * sheep * grass

• 羊 10

sheep
10

• b 羊的死亡率 0.01

b
0.01

• death 羊的死亡流 = 羊x 羊的死亡率

death
b * sheep

• 草 200

grass
200

• R 草的净萌发

R
100

grass_birth
R

c
0.002

grass_death
c * sheep * grass