Re: ODE with in a piece wise plot

*To*: mathgroup at smc.vnet.net*Subject*: [mg104243] Re: ODE with in a piece wise plot*From*: Hannes Kessler <HannesKessler at hushmail.com>*Date*: Sun, 25 Oct 2009 01:04:43 -0400 (EDT)*References*: <hbu7ps$7he$1@smc.vnet.net>

Hello Becky, I don't understand what you mean with "put in a ODE where the (x-1) is". Nevertheless, here is an example how one can use your function in an ODE: E1 = If[-1 <= x <= 0, 1, If[3 <= x <= 5, 2, If[-1 <= x <= 3= , (x - 1)]]] (* Equivalent but better looking *) E1=PiecewiseExpand[E1] (* Function definition using E1*) f[xx_] := E1 /. x :> xx (* Plot your function *) Plot[f[x], {x, -5, 5}] (* Use it as rhs in an ODE *) equation=y'[x] + y[x] == f[x] solution = NDSolve[{equation, y[-5] == 1}, y, {x, -5, 5}] (* The solution function and its plot *) yfunc = y /. First[solution] Plot[yfunc[x], {x, -5, 5}] By the way, you can enter a piecewise function definition similar to the one obtained by PiecewiseExpand by entering <escape>pw<esacpe> followed by one or more <ctrl>enter. Or use Piecewise[..] (look into the Mathematica help for Piecewise). Best regards, Hannes Kessler On 24 Okt., 08:45, "Becky" <noslow... at comcast.net> wrote: > Can this be done? > > First of all, a basic example and then what I want to change. > > E1=If[-1<=x<=0,1,If[3<=x<=5,2,If[-1<=x<=3,(x-1)]]] > Plot[E1,{x,-5,5}] > > The purpose of this was to join all three areas into one plot. > > Now! I want to put in a ODE where the (x-1) is. > > Is this possible, and if so, would you mind giving me an example?