*To*: mathgroup@smc.vnet.net*Subject*: [mg10422] Re: [mg10381] Why doesn't this work ?*From*: jpk@max.mpae.gwdg.de*Date*: Tue, 13 Jan 1998 02:07:23 -0500

Hi Andreas Plot has the attribute HoldAll. So: > Look at this: > > This works: > Clear[S1]; > S1=Sin[x]; > Plot[S1, {x, 0, 3}] > Matheamtica see one single symbol S1 and assumes it has to plot one function. S1 gets evaluated and evaluates to Sin[x] -- all works fine. > But why doesn't it work with more than one functions ? > > Clear[S2]; > S2={Sin[x],Cos[x]}; > Plot[S2, {x, 0, Pi}] Again Mathematica see one single symbol and assumes S2 will return one value. Now S2 gets evaluated and evaluates to a pair of functions -- but now it is to late to fall back from the assumption of one single argument and You get an error message. To Help You out -- Just put a Evaluate[S1] to Your first Plot[]-argument. Than S2 is evaluated first Plot[Evaluate[S2],{x,0,Pi}] to Plot[{Sin[x],Cos[x]},{x,0,Pi}] and Mathematica can reconize that more than one function is to be plotted. Hope that helps Jens