Re: Extracting DSolve[]'s solution
- To: mathgroup at christensen.cybernetics.net
- Subject: [mg369] Re: [mg359] Extracting DSolve[]'s solution
- From: wmm at chem.wayne.edu (Martin McClain)
- Date: Tue, 27 Dec 94 18:02:28 EST
>How do you extract the solution for DSolve[] ?
>
>---------------------------------------
>In[1]:= DSolve[y'[t]==a y[t], y[t], t]
> a t
>Out[1]= {{y[t] -> E C[1]}}
>---------------------------------------
>
>I desire y[t_] := Some_MMA_Function[Out[1]] to be C[1] Exp[a t].
>
>I know this is probably very simple and well known, so be gentle.
>
>Joseph McWilliams Wagner's music is better than it sounds.
>Nacogdoches, TX -- Mark Twain --
>mcwilljg at euler.sfasu.edu
If you want to see an expression as the answer, do this:
In[34]:= DSolve[y'[t]==a y[t],y[t],t];
y[t] /. Flatten[%] // InputForm
(*Flatten gets rid of the extra pair of braces,
% means "last output (even if suppressed)",
and // InputForm is just for e-mail *)
Out[34] = E^(a*t)*C[1]
If you really want to go directly to a function definition, you can do
this:
In[35]:= Clear[y];
DSolve[y'[t]==a y[t], y[t], t];
y[t_]:=Evaluate[ y[t] /. Flatten[%] ]
There is no screen output from this, but a function definition was stored
under y.
To see it:
In[36]:= ??y
Out[36]:= Global`y
y[t_] := E^(a*t)*C[1]
or perhaps more to the point, use it:
In[37]:= y[r] // InputForm
Out[37] = E^(a*r)*C[1]
Regards to everybody in Nacogdoches- Martin McClain