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MathGroup Archive 2005

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Re: problems plotting a derivative

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54541] Re: [mg54479] problems plotting a derivative
  • From: Chris Chiasson <chris.chiasson at gmail.com>
  • Date: Tue, 22 Feb 2005 04:24:45 -0500 (EST)
  • References: <200502210844.DAA27207@smc.vnet.net>
  • Reply-to: Chris Chiasson <chris.chiasson at gmail.com>
  • Sender: owner-wri-mathgroup at wolfram.com

Try this:
f[x_] := 2x^3;
ParametricPlot[Evaluate[{D[f[x], x], x^2}], {x, 0, 1}]
The derivative command didn't work because it tried to take the
derivative of f(somenumber) with respect to a number. This is like
trying to take the derivative of x with respect to three.


On Mon, 21 Feb 2005 03:44:47 -0500 (EST), J. K. Smith <rob at pi-overe.com> 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
> 
> 


-- 
Chris Chiasson
Kettering University
Mechanical Engineering
Graduate Student
1 810 265 3161


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