ODE45 error: must return a column vector.

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nashyshan 2015-6-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/222680-ode45-error-must-return-a-column-vector

评论： James Tursa 2015-6-6

I am getting this error in my code. but in the MATLAB documentation there is an example ( Example 3) where the vectors are given as input but it works just fine. Why is that I get an error in my code?

Ca_ER   = 10e-6; 
c0  = 2e-6;   
c1  = .185; 
v1  = 6;  
v2  = .11;
v3  = .09e6;
v4  = 1.2;
k3  = .1e-6;
a1 = 400e6;
a2 = 0.2e6;
a3 = 400e6;
a4 = 0.2e6;
a5 = 20e6;
b2 = .21;
d1 = 0.13e-6;
d2 = b2/a2;
d3 = 943.4e-9;
d4 = d1*d2/d3; 
d5 = 82.34e-9; 
IP= .5e-6; 
Ca=.001e-6:.01e-6:1e-6;
num=Ca.*IP.*d2;
deno= (Ca.*IP+ IP*d2+d1*d2+Ca.*d3).*(Ca+d5);
p_open=( num./deno).^3; %this is the vector input   
dc=@(t,c) (c1.*((v1.*p_open)+v2).*(Ca_ER-c))-((v3.*(c.^2))/(c.^2+(k3^2)));
[t,c]=ode45(dc,linspace(0, 100, 1000),.19e-6);
plot(t,c);

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Answer 1

James Tursa 2015-6-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/222680-ode45-error-must-return-a-column-vector#answer_181731

在 MATLAB Online 中打开

For a start, try changing to column vectors. E.g.,

Ca = (.001e-6:.01e-6:1e-6)';

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James Tursa 2015-6-6

编辑：James Tursa 2015-6-6

在 MATLAB Online 中打开

The myode function of Example 3 returns a scalar value for dydt. The vector stuff you see is just the inputs for the interpolation used to get the scalars. I.e., ode45 gets passed an anonymous function handle (that happens to use the vector stuff off to the side via myode) that takes a scalar input y and returns a scalar output ... it does not get passed the vector stuff directly.

Specifically, this is what is happening:

[T Y] = ode45(@(t,y) myode(t,y,ft,f,gt,g),Tspan,IC);

The @(t,y) creates an anonymous function handle with two inputs, t and y. In this case t and y are both scalars, and that is the only interface that ode45 knows about directly. That anonymous function calls another function, myode, with FIXED INPUTS ft, f, gt, and g which are all vectors. In essence, snapshots of ft, f, gt, and g are taken at the time this line is executed and embedded within the anonymous function handle itself (technically, shared data copies of ft, f, gt, and g are created and stored within the function handle). So each time this anonymous function gets called from within ode45, it ends up calling myode with t and y (passed directly in from ode45) but also uses these ft, f, gt, and g vectors at whatever state they happened to be in at the time of the anonymous function handle creation.

nashyshan 2015-6-6

编辑：nashyshan 2015-6-6

Okay! I will check and get back. Thank you so much for the valuable inputs.

James Tursa 2015-6-6

We don't know what problem you are trying to solve. Are you trying to solve a scalar 1st order differential equation? A scalar higher order differential equation? A vector DE? Or what? Tell us what the DE or system of DE's is.

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ODE45 error: must return a column vector.

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