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.
>
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