DDE23 - specifying which variables are delayed (2024)

% ExampleDDE - Matlab time dependent delay de

lags = [0.3 3]; % [y2 delay y4 delay]

tspan = [0 10];

param = [1 5 2 0.1 0.5 0.7]; % example parameters for DE

sol = dde23(@(t,y,z) ddefun(t,y,z,param), lags, @history, tspan);

plot(sol.x,sol.y,'-o')

xlabel('Time t');

ylabel('Solution y');

legend('y_1','y_2','y_3', 'y_4','Location','NorthWest');

function dydt = ddefun(t,y, Z, p)

y1 = y(1);

y2 = y(2);

y3 = y(3);

y4 = y(4);

ylag2 = Z(2,1); % this should be a delay on y2, first time lag

ylag4 = Z(4,2); % this should be a delay on y4, second time lag

lagged = ylag2/ylag4;

A = p(1);

B = p(2);

C = p(3);

a = p(4);

b = p(5);

d = p(6);

d1 = A* y1 + b * y3 - C * y4;

d2 = C * y4 + lagged * y3 - a * B * y4 - A * y1;

d3 = a * y4 - b * y3;

d4 = d * y4;

dydt = [d1;d2;d3;d4];

end

function s = history(t) % history function for t<= 0

s = [1 5 10 7];

end

Edited: Sanju 5 minutes ago