Conditional variables with running ODE45

Hi all, is it possible to call variables within an ODE45 and use if statements? So the general idea can be see in the code below, what I'm trying to do is that if the value of y(:,2) is greater than 0.3, than A will be 0.1 else, if its lower it will just run with a value of 0.1. Is this possible?

clear all, close all, clc

if y(:,2)>0.3
    A = 0.2;
else
    A = 0.1;
end

B = 0.1;

tspan = [0:4:200];
y0 = [0.95 0.05 0];
[t,y] = ode45(@(t,y)odefcn(y,A,B),tspan,y0);


figure(1)
hold on
plot(t,y(:,1),'-o')
plot(t,y(:,2),'-*')
plot(t,y(:,3),'-d')

function dydt = odefcn(y,A,B)
dydt = zeros(3,1);
dydt(1) = -A*y(2)*y(1);
dydt(2) = A*y(2)*y(1)-B*y(2);
dydt(3) = B*y(2);
end

Answer 1

[Alan Stevens]

Yes, but rearrange the coding as follows:

tspan = [0:4:200];
y0 = [0.95 0.05 0];
[t,y] = ode45(@(t,y)odefcn(t,y),tspan,y0);


figure(1)
hold on
plot(t,y(:,1),'-o')
plot(t,y(:,2),'-*')
plot(t,y(:,3),'-d')

function dydt = odefcn(~,y)
if y(2)>0.3
    A = 0.2;
else
    A = 0.1;
end

B = 0.1;
dydt = zeros(3,1);
dydt(1) = -A*y(2)*y(1);
dydt(2) = A*y(2)*y(1)-B*y(2);
dydt(3) = B*y(2);
end