from modsim import (TimeSeries, TimeFrame, System, State, linrange)
init = State(juveniles=0, adults=10)
system = System(init=init, t0 = 0, t_end=20, birth_rate=0.90,
mature_rate=0.33, death_rate=0.5)<<pre>>
def run_simulation(system):
"""Runs a proportional growth model.
Adds TimeSeries to `system` as `results`.
system: System object
"""
juveniles = TimeSeries()
juveniles[system.t0] = system.init.juveniles
adults = TimeSeries()
adults[system.t0] = system.init.adults
for t in linrange(system.t0, system.t_end):
maturations = system.mature_rate * juveniles[t]
births = system.birth_rate * adults[t]
deaths = system.death_rate * adults[t]
if adults[t] > 30:
market = adults[t] - 30
else:
market = 0
juveniles[t + 1] = juveniles[t] + births - maturations
adults[t + 1] = adults[t] + maturations - deaths - market
system.adults = adults
system.juveniles = juveniles<<run>>
run_simulation(system)
print(system.adults)
0 10.000000
1 5.000000
2 5.470000
3 6.209900
4 7.057723
5 8.021560
6 9.117031
7 10.362107
8 11.777219
9 13.385586
10 15.213601
11 17.291261
12 19.652658
13 22.336542
14 25.386953
15 28.853947
16 32.794414
17 34.478600
18 36.487431
19 37.893339
20 39.401924
21 40.546917
dtype: float64
<<pre>>
def run_simulation(system):
"""Runs a proportional growth model.
Adds TimeSeries to `system` as `results`.
system: System object
"""
frame = TimeFrame(columns=system.init.index)
frame.loc[system.t0] = system.init
for t in linrange(system.t0, system.t_end):
maturations = system.mature_rate * frame['juveniles'][t]
births = system.birth_rate * frame['adults'][t]
deaths = system.death_rate * frame['adults'][t]
if frame['adults'][t] > 30:
market = frame['adults'][t] - 30
else:
market = 0
frame.loc[t + 1] = [frame['juveniles'][t] + births - maturations,
frame['juveniles'][t] + maturations - deaths - market]
system.results = frame
run_simulation(system)
print(system.results) juveniles adults
0 0.000000 10.000000
1 9.000000 -5.000000
2 1.530000 14.470000
3 14.048100 -5.200100
4 4.732137 21.284023
5 22.326152 -4.348269
6 11.045080 31.867917
7 36.081329 -3.111920
8 21.373763 49.544128
9 58.910136 -15.889088
10 25.169612 86.295025
11 94.529162 -65.966953
12 3.964281 158.707262
13 145.492605 -202.788399
14 -85.029514 294.899364
15 208.439653 -525.438299
16 -333.239902 539.943888
17 262.678765 -1223.124901
18 -924.817639 960.925208
19 245.204869 -2641.395271
20 -2212.968481 1646.820111
21 -0.550783 -5383.478247
<<pre>>
def plot_results(sytsem):
system.results.plot()