Re: change the solution to a differential equation into a user defined function - question.nb (0/1)
- To: mathgroup at smc.vnet.net
- Subject: [mg15603] Re: change the solution to a differential equation into a user defined function - question.nb (0/1)
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Thu, 28 Jan 1999 04:23:31 -0500 (EST)
- Organization: Universitaet Leipzig
- References: <786u4u$29b@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi Young
lets stat with Your example:
sol=DSolve[y'[x]==x,y[x],x]
To make a pattern for the solution we have to do replace y[x] by y[x_]
and -> by := so we can write down
holdsol=(Hold /@
Flatten[sol/.
HoldPattern[Rule[z_,b_]] :>
Rule@@ {z /. x-> Pattern[x,Blank[]],b}]) /. Rule
->SetDelayed
The result is a list of function definitions enclosed by Hold and you
have to
decide which solution you want. If there is only one solution you can
make type
ReleaseHold[
holdsol[[1]]
]
and see that you have the defintion for the pattern y[x_]
Hope that helps
Jens
Yong Cai wrote:
>
> I probably have to apologize for the awkward name for the subject.
>
> My question is
> When I define the same function for y[x] by myself, it is evidently a
> pattern where x can be taken in any value.
>
> Then comes the question: how can we use the solution given in a
> differential equation which itself is a function as a function for
> later use?
>
> It seems to be straightforward, but I have looked through the
> Mathematica Book and found no clue. Your help will be greatly
> appreciated.