Vector length must be the same

Could someone help me find what I did wrong?

I am trying to plot two system ODE in matlab, but the system shows error in vector length? I do not get what is wrong~

Here is my code:

tRange = [0,300];
concA0=1.2;
concB0=0.2;
concC0 = 1.2; concD0 = 1.2; concE0 = 1.2;
Y0=[concA0;concB0];
X0=[concC0;concD0;concE0];
[t,Y]=ode45(@first,tRange,Y0);
[t,X]=ode45(@second,tRange,X0);
concA=Y(:,1);
concB=Y(:,2);
concC=X(:,1);
concD=X(:,2);
concE=X(:,3);
hold on
plot(t,concA,'k-')
plot(t,concB,'b-')
hold off

plot(t,concC,'r-')
plot(t,concD,'m-')
plot(t,concE,'g-')

function dYdt = first(t,Y)
concA = Y(1);
concB = Y(2);
dAdt=-2.3*power(10,-3).*power(concA,4);
dBdt=2.3*power(10,-3).*power(concA,4);
dYdt=[dAdt;dBdt];
end

function dXdt = second(t,X)
 concC = X(1);
 concD = X(2);
 concE = X(3);
 dCdt=-8.5*power(10,-4).*concC.*power(concD,2);
 dDdt=-2*8.5*power(10,-4).*concC.*power(concD,2);
 dEdt=8.5*power(10,-4).*concC.*power(concD,2);
 dXdt=[dCdt;dDdt;dEdt];
end

[Walter Roberson]

MATLAB is not able to execute pictures of code and it is too much trouble to OCR the image.

[Stephen23]

"Could someone help me find what I did wrong?"

You uploaded images of code, instead of the code iteself.

Answer 1

[madhan ravi]

tRange = [0,300];
concA0=1.2;
concB0=0.2;
concC0 = 1.2; concD0 = 1.2; concE0 = 1.2;
Y0=[concA0;concB0];
X0=[concC0;concD0;concE0];
[t1,Y]=ode45(@first,tRange,Y0);
% ^--- name it different from another t
[t,X]=ode45(@second,tRange,X0);
concA=Y(:,1);
concB=Y(:,2);
concC=X(:,1);
concD=X(:,2);
concE=X(:,3);
plot(t1,concA,'k-')
hold on
plot(t1,concB,'b-')
plot(t,concC,'r-')
plot(t,concD,'m-')
plot(t,concE,'g-')

function dYdt = first(t,Y)
concA = Y(1);
concB = Y(2);
dAdt=-2.3*power(10,-3).*power(concA,4);
dBdt=2.3*power(10,-3).*power(concA,4);
dYdt=[dAdt;dBdt];
end

function dXdt = second(t,X)
 concC = X(1);
 concD = X(2);
 concE = X(3);
 dCdt=-8.5*power(10,-4).*concC.*power(concD,2);
 dDdt=-2*8.5*power(10,-4).*concC.*power(concD,2);
 dEdt=8.5*power(10,-4).*concC.*power(concD,2);
 dXdt=[dCdt;dDdt;dEdt];
end

[Jingyu Kan]

Thanks so much! I guessed this was the problem!

Answer 2

[Walter Roberson]

When you pass a vector of two elements to ode45 as the time range then the number of entries it uses in the output is whatever it feels like using in order to get a result with the required error tolerance . That happens to end up being a different number for first than for second so the t returned for first is not the same length as for second but your code treats the two as if they were the same length and same values .