# Why do i get a blank graph?

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jpmontoya 1 Jun 2019
댓글: jpmontoya 2 Jun 2019
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
##### 댓글 수: 1표시숨기기 없음
Walter Roberson 2 Jun 2019
It would help to have your osc function

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### 채택된 답변

gonzalo Mier 2 Jun 2019
편집: gonzalo Mier 2 Jun 2019
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,'*')
##### 댓글 수: 3표시숨기기 이전 댓글 수: 2
jpmontoya 2 Jun 2019
Thank you so much. I did a lot of things considering the answers of Gonzalo and Walter and finally everything works perfect.

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