MATLAB: Can’t i plot a graph for a against t

plottingsymbolicwhile loop

k_n= 7*10^-11;
n= 2;
i=1;
t(i)=0; %in hours
a = sym('a')
while t<=2.5 %2.5hours
    
    a= 1-exp(-k_n*(t(i))^n); %degree of hydration
    
    dt=1/3600; %1sec interval
    t(i+1)=t(i)+dt;
    i=i+1;
    
end
figure(1);
plot(t,a,'r'),xlabel('t [h]'),ylabel('degree of hydration');
hold on;

Best Answer

k_n= 7*10^-11;
n= 2;
dt=1/3600; %1sec interval
t=0:dt:2.5;
a= 1-exp(-k_n*(t).^n); %degree of hydration
t=0:dt:2.5;
figure(1);
plot(t,a,'r'),
xlabel('t [h]')
ylabel('degree of hydration')

Related Solutions

MATLAB: How to plot these for loops

Put them all in subplots, with the appropriate indexing:

tspan = linspace(0, 5, 25);
for k=1:5
y0 = 0;
[t,y(:,k)] = ode45(@(t,y) k*t, tspan, y0);
subplot(4,1,1)
title('Exponential Model')
grid on
end
plot(t,y,'-o')
% tspan = [0 5];


r=1;
for k=1:5
y0 = 0;
[t,y(:,k)] = ode45(@(t,y) r*(1-t/k)*t, tspan, y0);
% hold on

title('Logistic Model')
grid on
end
subplot(4,1,2)
plot(t,y,'-o')
% tspan = [0 5];
r=1;
k=1;
for H=1:5
y0 = 0;
[t,y(:,H)] = ode45(@(t,y) r*(1-t/k)*t-H, tspan, y0);
title('Constant Harvesting')
% hold on
grid on
end
subplot(4,1,3)
plot(t,y,'-o')
% tspan = [0 5];
r=1;
k=1;
H=1;
for A=1:5
y0 = 0;
[t,y(:,A)] = ode45(@(t,y) r*(1-t/k)*t-H*(t/(A+t)), tspan, y0);
title('Population dependent Harvesting')
hold on
grid on
end
subplot(4,1,4)
plot(t,y,'-o')

I also defined ‘tspan’ as a vector of 25 elements so it would be straightforward to save them to matrices, then plot them.

MATLAB: I need help solving an ODE using the Runge Kutta method. The values I obtain for “A” are correct, but the value I receive for “C” are incorrect.

Your signature of the derivative function is f2(A,C,t) not f2(A,t,C). So these lines:

    k6(k) = dt*f2((A(k)+0.5*k1(k)),t(k)+0.5*dt,C(k)+0.5*k5(k));
    k7(k) = dt*f2((A(k)+0.5*k2(k)),t(k)+0.5*dt,C(k)+0.5*k6(k)); 
    k8(k) = dt*f2((A(k)+k3(k)),t(k)+dt,C(k)+k7(k));

should probably be these instead:

    k6(k) = dt*f2((A(k)+0.5*k1(k)),C(k)+0.5*k5(k),t(k)+0.5*dt);
    k7(k) = dt*f2((A(k)+0.5*k2(k)),C(k)+0.5*k6(k),t(k)+0.5*dt); 
    k8(k) = dt*f2((A(k)+    k3(k)),C(k)+    k7(k),t(k)+    dt);

Best Answer

Related Solutions

MATLAB: How to plot these for loops

MATLAB: I need help solving an ODE using the Runge Kutta method. The values I obtain for “A” are correct, but the value I receive for “C” are incorrect.

Related Question