2019-11-19-203045.sagews

#3.3 Further Exercise #1-d
var("J","R")
t=srange(0,20,1)
sol=desolve_odeint([-R, J-0.1*R], ics=[10,10],dvars=[J,R], times=t)
list_plot(zip(sol[:,0],sol[:,1]), axes_labels=["J","R"], plotjoined=true)

(J, R)

#3.3 Further Exercise #1-e
var("J","R")
t=srange(0,20,1)
sol=desolve_odeint([-R, J-0.1*R], ics=[2,5],dvars=[J,R], times=t)
list_plot(zip(sol[:,0],sol[:,1]), axes_labels=["J","R"], plotjoined=true)

(J, R)

var("J","R")
t=srange(0,20,1)
sol=desolve_odeint([-R, J-0.1*R], ics=[1,1],dvars=[J,R], times=t)
list_plot(zip(sol[:,0],sol[:,1]), axes_labels=["J","R"], plotjoined=true)

(J, R)