       Re: Plotting a x,y,z function

• To: mathgroup at smc.vnet.net
• Subject: [mg98702] Re: Plotting a x,y,z function
• From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
• Date: Thu, 16 Apr 2009 04:17:58 -0400 (EDT)
• References: <gs47lm\$7p3\$1@smc.vnet.net>

```Of course you have to specify that r = Sqrt[x^2+y^2+z^2]. r is just a
letter that sometimes is used to denote radius but it may serve
millions of other purposes. How do you think Mathematica could guess
what you're using it for?

r[x_, y_, z_] = Sqrt[x^2 + y^2 + z^2];
f[x_, y_, z_] = (x^2 + y^2 + z^2) E^-(r[x, y, z]^2/2);

ContourPlot3D[f[x, y, z], {x, -10, 10}, {y, -10, 10}, {z, -10, 10}]

In your definition of f you used the lowercase e which hasn't a
special meaning, use esc-ee-esc or E instead.

Cheers -- Sjoerd

On Apr 15, 10:59 am, chem_chick <raeanne.napol... at gmail.com> wrote:
> I needed help plotting the following function:
>
> f[x_,y_,z_] = (x^2+y^2+z^2) e^-(r^2/2)
>
> ContourPlot3D[(x^2 + y^2 - z^2) Exp[-r^2/2], {x, -10, 10}, {y, -10,
>   10}, {z, -10, 10}]
>
> does not work because it doesn't understand what r (radius) is....what
> is the keyword/whatever for radius?  Or do I have to define r in terms
> of x,y,z somehow?!   Help with syntax will be great!
>
> Thanks!

```

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