Re: Problem using Evaluate[] inside a Plot command. 5.1

*To*: mathgroup at smc.vnet.net*Subject*: [mg54212] Re: Problem using Evaluate[] inside a Plot command. 5.1*From*: Nasser Abbasi <nma at 12000.org>*Date*: Sun, 13 Feb 2005 22:17:01 -0500 (EST)*References*: <cu78ub$me9$1@smc.vnet.net> <cumor4$3rc$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

D Herring wrote: > Hi Nasser, > > Maybe Evaluate[OutputResponse[sys,UnitStep[t], t]] is returning a value > which needs to be Evaluate[]d again before it can be plotted? > > I've never had your problem (don't even have the control toolbox), but > maybe > > Plot[{t2, Evaluate[Evaluate[OutputResponse[sys,UnitStep[t], t]]]}, > {t, 0, 3}, PlotRange -> All] > > might work? > > Your error message, "plot::plnr: .... is not a machine-size real > number at t=...." usually indicates the need to Evaluate[] one of the > Plot[] arguments. > > Good luck, > Daniel > Daniel; I tried your command above (You had a typo, 't2' should be 't^2' or just 't'), any way, it does not work either. I am sure this is a bug in Mathematica, either the kernel or the ControlSystems toolbox or the parser. It does not make sense for this command to work: Plot[ Evaluate[OutputResponse[sys, UnitStep[t], t]] , {t, 0, 3}, PlotRange -> All] But if I now simply combine another function in the plot command, so to plot 2 functions together, it will now fail: Plot[ {t^2, Evaluate[OutputResponse[sys, UnitStep[t], t]] }, {t, 0, 3}, PlotRange -> All] "plot::plnr: .... is not a machine-size real Why would the second example above fail but the first not fail? btw, the output from the OutputResponse[] is simply a list that contains a function of t, such as { Exp[t/2] Cos[t] } So, nothing too complicated here. bye, Nasser