Finding specific data point x for given y

Here is my code, it works and the graph is correct. However, i am having trouble answering one of my questions about this code. I need to find the CB and CS values at t=5, as well as i need to find the t and CB values when CS = 0.001. I cannot figure out the codes to find those answers.

t = [0 50]; %time interval

Y0 = [0.05 5]; % initial values

[tout, Yout] = ode15s(@func20,t,Y0)

plot(tout,Yout)

xlabel('t')

ylabel('C')

legend('CB','CS')

title('HW 10 - Part4 ODE15s')

function dy = func20(t,x)

Kr = 0.30000;

K = 0.00300;

CB = x(1);

CS = x(2);

dy = zeros(2,1);

dy(1) = ((Kr)*(x(1))*(x(2)))/(K+x(2));

dy(2) = ((-0.75)*(Kr)*(x(1))*(x(2)))/(K+x(2));

end

Answer 1

[darova]

• I need to find the CB and CS values at t=5

Use interp1 to find

• i need to find the t and CB values when CS = 0.001

Use fsolve or fzero

FCS = @(x) interp1(tout,CS,x)-0.001;
t001 = fsolve(FCS,tinit);                % try: tinit = 15