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How to use ode() solver

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John Miller
John Miller 2012-6-24
关闭： MATLAB Answer Bot 2021-8-20
Hello, I have following code:
ftod_sym=detofJac(doy); %here I calculate my symbolic vectorfield ftod_sym which is a function of y1 y2 and t
myfun = matlabFunction(ftod_sym); %conversion
[T N]=ode15s(@(y,t)myfun,tspan,n0,optionsO); % n0 is a vector with 2 elements
I get following ERROR:
Error using odearguments (line 93)
@(Y,T)MYFUN returns a vector of length 1, but the length of initial conditions vector is 2. The vector returned
by @(Y,T)MYFUN and the initial conditions vector must have the same number of elements.
Error in ode15s (line 149)
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...
Error in flipflop_NR (line 46)
[T N]=ode15s(@(y,t)myfun,tspan,n0,optionsO);
Thank You

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回答（1 个）

Walter Roberson
Walter Roberson 2012-6-24
[T N]=ode15s(myfun,tspan,n0,optionsO);
You were not passing y and t to myfun, so you were not getting back the output you were expecting.
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Walter Roberson
Walter Roberson 2012-6-24
Use subscripting of "y" right in your symbolic expression, and then just use myfun as the function handle.
John Miller
John Miller 2012-6-24
For my symbolic expression I need for example the symbolic jacobian. What I do is:
y=sym('y',[2 1]);
syms t
f_algebraic=ALG_y(t,y); %my function
J = jacobian(f_algebraic, y);
I dont know how to do in another way...
Hope somone can help
Thank you

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