Re: problems plotting a derivative

*To*: mathgroup at smc.vnet.net*Subject*: [mg54495] Re: [mg54479] problems plotting a derivative*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Tue, 22 Feb 2005 04:22:53 -0500 (EST)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

Put the Evaluate around the entire first argument: f[x_]:=2x^3; ParametricPlot[Evaluate[{D[f[x],x],x^2}],{x,0,1}]; Bob Hanlon > > From: "J. K. Smith" <rob at pi-overe.com> To: mathgroup at smc.vnet.net > Date: 2005/02/21 Mon AM 03:44:47 EST > To: mathgroup at smc.vnet.net > Subject: [mg54495] [mg54479] problems plotting a derivative > > I've tried a lot of ways but nothing has worked so far. > The following statements are my problem simplified: > > f[x_] := 2x^3; > ParametricPlot[{D[f[x], x], x^2}, {x, 0, 1}] > > When I run this I get error messages griping about numbers not being > valid variables but it doesn't end up plotting anything. In this example > I should see a straight line. > > I've tried using Evaluate[ D[f[x],x] ] and lots of other schemes which > seemed to work in the past but I can't get ParametricPlot to digest any > of them. Something about the result of that derivative doesn't yield > something that can be plotted. But I don't know what property it is. > > Would you kind Mathematica gurus please get me thru this one (too)? > > Thanks. > > remove the dash if emailing > >