dsolve - doesn't work inside a function.

How can I solve: dx/dt = f(t,x) , x(t_0) = x_0 using dsolve? (or in any other symbolic way)

If I try typing for example: dsolve('Dx = t^2/x', 'x(0)=1') then everything is ok.

But if I try: f = @(t,x) t^2/x; dsolve('Dx = f', 'x(0)=1') - it doesn't work.

I need this to define some function[] = name(f,...) using dsolve.

Could someone help me?

Answer 1

[Walter Roberson]

dsolve() only operates on symbolic functions or symbolic expressions, and does not operate on anonymous functions or inline functions.

The expression syntax is different for symbolic functions vs anonymous functions or inline functions, so you cannot use char() to convert the anonymous function to its MATLAB equivalent.

What you need is:

syms t x
ftx = f(t,x);  %pass symbolic arguments to the anonymous function!
dfun = subs(sym('Dx = FTX'), 'FTX', ftx);
dsolve(dfun, sym('x(0)=1'))

Answer 2

[Kamil]

function[ ] = fun(f)
syms t x
ftx = f(t,x);  %pass symbolic arguments to the anonymous function!
dfun = subs(sym('Dx = FTX'), 'FTX', ftx);
dsolve(dfun, sym('x(t0)=x0'))

end

And I'm still getting:

> In dsolve at 92 In fun at 5

ans =

[ empty sym ]

[Walter Roberson]

dfun_init = subs(sym('x(t0)=x0'), {'t0', 'x0'}, {t0, x0}));

dsovle(dfun, dfun_init);