Re: How do I get a DSolve'd function

*To*: mathgroup at smc.vnet.net*Subject*: [mg54397] Re: How do I get a DSolve'd function*From*: highegg at centrum.cz (highegg)*Date*: Sun, 20 Feb 2005 00:07:55 -0500 (EST)*References*: <bri4oj8p6w4b@legacy>*Sender*: owner-wri-mathgroup at wolfram.com

On 18 Feb 05 20:11:37 -0500 (EST), 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[0]==10},f,x] >Plot[f/.sol,{x,0,10}] > >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? Hello, that's because DSolve (like all Solve statements) always generates a list of solutions, even if there's a single one. You must therefore extract the one you are interested in by doing f /. First[sol] this gives you the function. f/. sol gives you a list of functions. regards, Jaroslav