models/johnpye/lotka.a4c

REQUIRE "ivpsystem.a4l";
REQUIRE "atoms.a4l";

(*
	A simple population model using the Lotka-Volterra model.
	
	http://www.stolaf.edu/people/mckelvey/envision.dir/lotka-volt.html
	http://www.ento.vt.edu/~sharov/PopEcol/lec10/lotka.html
*)
MODEL lotka;

	R IS_A factor; (* rabbits *)
	F IS_A factor; (* foxes *)
	
	dR_dt IS_A rate;
	dF_dt IS_A rate;

	r IS_A rate; (* growth rate of rabbits in absence of foxes *) 
	a IS_A rate; (* efficiency of turning hunted rabbits into new foxes*)
	b IS_A rate; (* production rate of predators per prey eaten *)
	m IS_A rate; (* natural fox mortality rate *)
	
	dR_dt = r*R - a*R*F;
	dF_dt = b*R*F - m*F;
	
	t IS_A time;	
METHODS

METHOD on_load;
	RUN default_self;
	RUN reset; RUN values;
	RUN set_obs;
	RUN set_ode;
END on_load;

METHOD default_self;
	R := 1000;
	F := 9;
	dR_dt := 0 {Hz};
	dF_dt := 0 {Hz};
END default_self;

METHOD specify;
	FIX r,a,b,m;
	FIX F,R;
END specify;

METHOD values;
	r	:= 0.04 {1/s};
	a	:= 0.0005 {1/s};
	b	:= 0.1*0.0005 {1/s};
	m	:= 0.2 {1/s};
	t   := 0{s};
END values;

METHOD set_obs;
	t.obs_id :=1;
	R.obs_id :=2;
	F.obs_id :=3;
END set_obs;

METHOD set_ode; (* this is where the current implementation sux *)
	FREE F,R,dR_dt,dF_dt;

	R.ode_id := 1;   R.ode_type := 1;
	dR_dt.ode_id := 1; dR_dt.ode_type := 2;
	
	F.ode_id := 2; F.ode_type := 1;
	dF_dt.ode_id := 2; dF_dt.ode_type := 2;

	t.ode_type :=-1;
END set_ode;


END lotka;
1	REQUIRE "ivpsystem.a4l";
2	REQUIRE "atoms.a4l";
3
4	(*
5	A simple population model using the Lotka-Volterra model.
6
7	http://www.stolaf.edu/people/mckelvey/envision.dir/lotka-volt.html
8	http://www.ento.vt.edu/~sharov/PopEcol/lec10/lotka.html
9	*)
10	MODEL lotka;
11
12	R IS_A factor; (* rabbits *)
13	F IS_A factor; (* foxes *)
14
15	dR_dt IS_A rate;
16	dF_dt IS_A rate;
17
18	r IS_A rate; (* growth rate of rabbits in absence of foxes *)
19	a IS_A rate; (* efficiency of turning hunted rabbits into new foxes*)
20	b IS_A rate; (* production rate of predators per prey eaten *)
21	m IS_A rate; (* natural fox mortality rate *)
22
23	dR_dt = rR - aR*F;
24	dF_dt = bRF - m*F;
25
26	t IS_A time;
27	METHODS
28
29	METHOD on_load;
30	RUN default_self;
31	RUN reset; RUN values;
32	RUN set_obs;
33	RUN set_ode;
34	END on_load;
35
36	METHOD default_self;
37	R := 1000;
38	F := 9;
39	dR_dt := 0 {Hz};
40	dF_dt := 0 {Hz};
41	END default_self;
42
43	METHOD specify;
44	FIX r,a,b,m;
45	FIX F,R;
46	END specify;
47
48	METHOD values;
49	r := 0.04 {1/s};
50	a := 0.0005 {1/s};
51	b := 0.1*0.0005 {1/s};
52	m := 0.2 {1/s};
53	t := 0{s};
54	END values;
55
56	METHOD set_obs;
57	t.obs_id :=1;
58	R.obs_id :=2;
59	F.obs_id :=3;
60	END set_obs;
61
62	METHOD set_ode; (* this is where the current implementation sux *)
63	FREE F,R,dR_dt,dF_dt;
64
65	R.ode_id := 1; R.ode_type := 1;
66	dR_dt.ode_id := 1; dR_dt.ode_type := 2;
67
68	F.ode_id := 2; F.ode_type := 1;
69	dF_dt.ode_id := 2; dF_dt.ode_type := 2;
70
71	t.ode_type :=-1;
72	END set_ode;
73
74
75	END lotka;