Re: problems plotting a derivative

*To*: mathgroup at smc.vnet.net*Subject*: [mg54520] Re: [mg54479] problems plotting a derivative*From*: "David Park" <djmp at earthlink.net>*Date*: Tue, 22 Feb 2005 04:23:38 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

You have to Evaluate the entire parametrization. ParametricPlot[{D[f[x], x], x^2} // Evaluate, {x, 0, 1}] Or you could use... ParametricPlot[{f'[x], x^2}, {x, 0, 1}] David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: J. K. Smith [mailto:rob at pi-overe.com] To: mathgroup at smc.vnet.net 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