ODE45 error must return column vector

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Brianna Biondo
Brianna Biondo 2023-3-11
评论： Walter Roberson 2023-3-11
Ran in:
No matter what I do I keep receiving the error of a column vector. I have tried making it all zeros first befort completing the function to create a column vector but nothing is working. Any insight would be helpful.
CO(2,1) = 10;
tRange(2,1) = 10;
[tSol,CSol] = ode45(@ConvFunction,tRange,CO);
Error using odearguments
CONVFUNCTION must return a column vector.

Error in ode45 (line 107)
odearguments(odeIsFuncHandle,odeTreatAsMFile, solver_name, ode, tspan, y0, options, varargin);
plot(tSol,CSol(:,1))
function F = ConvFunction(t,~)
CaO=10;
k1=.45;
k2=.05;
Ca=CaO*exp(-t*(k1+k2));
dCadt=-(k1*(Ca)-(k2*(Ca)));
dCbdt=k1*(Ca);
dCcdt=k2*(Ca);
dFdt = zeros(3,1);
dFdt = [dCadt dCbdt dCcdt];
F= dFdt;
end

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采纳的回答

Paul
Paul 2023-3-11
Try doing what the error message says and make sure that F is a column vector. Here's one option
dFdt = [dCadt ; dCbdt ; dCcdt];
Also, the code is only specifying two initial conditions. It needs to specify three.
  2 个评论
Brianna Biondo
Brianna Biondo 2023-3-11
编辑：Brianna Biondo 2023-3-11
Ran in:
Thank you for the help, im getting this as an answer now. Sorry I am newer to matlab and am getting really confused.
CO(2,1) = 10;
tRange(2,1) = 10;
[tSol,CSol,~] = ode45(@ConvFunction,tRange,CO);
Error using odearguments
CONVFUNCTION returns a vector of length 3, but the length of initial conditions vector is 2. The vector returned by CONVFUNCTION and the initial conditions vector must have the same number of
elements.

Error in ode45 (line 107)
odearguments(odeIsFuncHandle,odeTreatAsMFile, solver_name, ode, tspan, y0, options, varargin);
plot(tSol,CSol(:,1))
function F = ConvFunction(t,~,~)
CaO=10;
k1=.45;
k2=.05;
Ca=CaO*exp(-t*(k1+k2));
dCadt=-(k1*(Ca)-(k2*(Ca)));
dCbdt=k1*(Ca);
dCcdt=k2*(Ca);
dFdt = zeros(3,1);
dFdt = [dCadt;dCbdt;dCcdt];
F= dFdt;
end
Walter Roberson
Walter Roberson 2023-3-11
Unless you have assigned something to CO before this,
CO(2,1) = 10;
creates CO as a column vector with exactly two values. You are passing that vector of length 2 as the initial state. You ignore the state inside ConvFunction and return a vector of length 3 . The length of the vector you return must be the same as the number of input values.

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