Re: Re: What to do in v. 6 in place of

• To: mathgroup at smc.vnet.net
• Subject: [mg76941] Re: [mg76829] Re: What to do in v. 6 in place of
• From: "Chris Chiasson" <chris at chiasson.name>
• Date: Wed, 30 May 2007 05:26:52 -0400 (EDT)
• References: <f3bh1e\$37g\$1@smc.vnet.net> <200705280500.BAA15752@smc.vnet.net>

```You could put Bob's code in a package and use a DownValue with a
Condition to overload Plot, but that would only work where you have
control over the Mathematica installation.

On 5/28/07, Helen Read <hpr at together.net> wrote:
> Bob Hanlon wrote:
> > This works for simple cases such as your examples.
> >
> > Clear[realPlot];
> > realPlot[expr_,
> >    {x_Symbol, xmin_?NumericQ, xmax_?NumericQ},
> >    opts___] := Module[{d, e, f, y},
> >    e = Flatten@{expr};
> >    d = (Denominator@PowerExpand@Log[x, #] & /@ e);
> >    f = y /. (ToRules@
> >          Reduce[y^#[[2]] == PowerExpand[#[[1]]^#[[2]]],
> >           y, Reals] & /@ Thread[{e, d}]);
> >    Plot[f, {x, xmin, xmax}, opts]];
> >
> > Grid[{{realPlot[x^(1/3), {x, -8, 8}],
> >    realPlot[x^(3/5), {x, -8, 8}]},
> >   {realPlot[{x^(1/3), x^(3/5)}, {x, -8, 8}]}}]
>
> This completely misses the point, which is to make it easy for beginning
> calculus students to plot functions such as x^(1/3) for negative x.
> There is no way they could follow what you have written, let alone
> reproduce it themselves.
>
> Probably the best solution at this point is to simply use the old
> Miscellaneous`RealOnly` package when this comes up in class, and just
> ignore the "obsolete package" message.
>
> --
> University of Vermont
>
>

--
http://chris.chiasson.name/

```

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