MATLAB: Do i get a blank graph

blank graphplot

Hello, as you can see in the code below I am trying to make two plots but the problem is that the subplot (2,1,2) goes blank. I got nothing. I think maybe there is something wrong with the variables k1 and v1 since they depend on X(1) and X(3) which come from the solution of an ODE. Can somebody help me? Thanks in advance.
function [T,X] = call_osc()
tspan = [0 2000];
x1_0=0.05;
x2_0=0.05;
x3_0=298.15;
x4_0=0.1;
odeset('RelTol', 1e-10, 'AbsTol', 1e-12);
[T,X]=ode15s(@osc,tspan,[x1_0 x2_0 x3_0 x4_0]);
R=8.314;
Ea1=80000;
alpha=11;
A=1;
k1= 0.8*exp(-Ea1/(alpha*R*X(3)));
v1=k1*A*X(1);
subplot(2,1,1)
plot(T,X(:,3))
grid on
xlabel('tiempo(s)','Fontsize',13,'FontWeight','Bold')
ylabel('Temperatura (K)','Fontsize',13,'FontWeight','Bold')
subplot(2,1,2)
plot(X(:,1),v1)
grid on
end

Best Answer

  • You are computing v1 as
    k1= 0.8*exp(-Ea1/(alpha*R*X(3)));
    v1=k1*A*X(1);
    v1 is a matriz of size 1x1. So when you do plot( "vector of size 1xn" , "cte" ) the output is an empty plot.
    Check if the way to compute v1 is correct or you have to use X(:,1).
    PD: You also can check this doing:
    plot(X(:,1),v1,'*')