       Re: How do I get a DSolve'd function

• To: mathgroup at smc.vnet.net
• Subject: [mg54395] Re: How do I get a DSolve'd function
• From: Peter Pein <petsie at arcor.de>
• Date: Sun, 20 Feb 2005 00:07:54 -0500 (EST)
• References: <cv6t29\$6su\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Skirmantas wrote:
> I hope this is the last question for now.
>
> I can solve a differential equation and plot it by doing something
> like this:
>
> sol=DSolve[{f'[x]==-3f[x],f==10},f,x]
> Plot[f/.sol,{x,0,10}]
This will not work.
>
> But how do I get the function f[x] itself? I want to be able to input
> f[x] and get its definition. Or do Plot[f[x],{x,0,10}]. Or define
> y[x_]:=f[x]^2.
>
> f[x]/.sol or f[x_]:=f[x]/.sol or f[x_]:=sol[[n,n,n]] do not work.
>
> What if the solution is a function with many variables, say u[x,y,z]?
> What's the correct way to "get" it?
>
Try the usual way for ReplaceAll:

f=f/.sol

and now you can use f like any other function.

Oh, in the multivariate case, you should use u instaed of f:

u=u/.sol

--
Peter Pein
Berlin

```

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