From inline to anonymous function

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Francesco Wanderlingh
编辑： Alfonso Nieto-Castanon 2015-5-13
Hello, I've been struggling in trying to migrate the following inline function (which serves as an input to ode45), to an anonymous function. The function is the following:
g = inline(sprintf('[%s; %s]', dx1dt, dx2dt), 't', 'x');
which I merelely converted to:
g = @(t,x) sprintf('[%s; %s]', dx1dt, dx2dt);
I tried a couple of combinations but it seems like, after the @(t,x), the sprintf part does not get evaluated. I think I'm missing something, how I should I solve this?
Edit: Some clarification about the context.
The dx1dt and dx2dt are symbolic functions, and using the inline function the output is the following:
>> g
%Inline function:
% g(t,x) = [x(2); -(2943*cos(x(1)))/200]

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回答（3 个）

Star Strider
Star Strider 2015-5-13
编辑：Star Strider 2015-5-13
Completely guessing here (because the ‘dx1dt’ and ‘dx2dt’ aren’t shown).
See if this works:
g = @(t,x) [dx1dt(t,x), dx2dt(t,x)];
You may need to experiment with that, perhaps:
g = @(t,x) [dx1dt(t,x); dx2dt(t,x)];
instead, depending on what your functions are and what size vectors they return.
EDIT —
Your ODE function then becomes:
g = @(t,x) [x(2); -(2943*cos(x(1)))/200];
That should work in ode45 (or whatever solver you are using) without further modification.
Walter Roberson
Walter Roberson 2015-5-13
g = matlabFunction([dx1dt, dx2dt], [t,x]);
Alfonso Nieto-Castanon
编辑：Alfonso Nieto-Castanon 2015-5-13
if you have the symbolic toolbox:
g = matlabFunction(sprintf('[%s; %s]', dx1dt, dx2dt));
otherwise your best bet is probably something like:
g = eval(sprintf('@(%s)[%s;%s]',strjoin(symvar(dx1dt),','),dx1dt,dx2dt));
or perhaps simply:
g = eval(sprintf('@(t,x)[%s;%s]',dx1dt,dx2dt));

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