close all
clc
clear all
eqn1 = 'DR == a*J';
eqn2 = 'DJ == b*R';
inits = 'R(0) = 0.5, J(0) = 0.5';
solv = dsolve(eqn1,eqn2,inits,'t');




t = linspace(0,100,1e4);

a = 0.2;
b = 0.4;


R = eval(vectorize(solv.R));
J = eval(vectorize(solv.J));


figure(1)

plot(t,R,'b');
hold on
plot(t,J,'r');
grid on