Re: problems plotting a derivative

*To*: mathgroup at smc.vnet.net*Subject*: [mg54593] Re: problems plotting a derivative*From*: "Ray Koopman" <koopman at sfu.ca>*Date*: Wed, 23 Feb 2005 03:13:05 -0500 (EST)*References*: <cvc80j$qqu$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

f[x_] := 2x^3; g[x_] := Evaluate[D[f[x], x]]; ParametricPlot[{g[x], x^2}, {x, 0, 1}] works fine for me. J. K. Smith wrote: > 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