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Re: A 3D Plot Query

  • To: mathgroup at smc.vnet.net
  • Subject: [mg94267] Re: A 3D Plot Query
  • From: "sjoerd.c.devries at gmail.com" <sjoerd.c.devries at gmail.com>
  • Date: Tue, 9 Dec 2008 07:00:12 -0500 (EST)
  • References: <ghj01t$ff8$1@smc.vnet.net>

Plot3D[2 - (x^2 + y^2), {x, -1, 1}, {y, -1, 1}, Boxed -> False,
 AxesOrigin -> {0, 0, 0}, AspectRatio -> 1]

shows the three axes. In M6/7 you can rotate them with your mouse to
your liking. Couldn't get it to draw axis for the first quadrant only,
though. In M7 you could draw some Arrow graphics and generate the axes
that way.

You can make it more cap-like in this way:

Plot3D[2 - (x^2 + y^2), {x, -1, 1}, {y, -1, 1}, Boxed -> False,
 AxesOrigin -> {0, 0, 0}, AspectRatio -> 1,
 RegionFunction -> Function[{x, y, z}, x^2 + y^2 < 1]]

Strangely, this hides the x and y-axes. Looks like a bug.

Cheers -- Sjoerd


On Dec 8, 1:22 pm, pcoord... at gmail.com wrote:
> Hi,
>
> This may sound silly, but I can't get it to work. (I'm using v 6.0)
>
> How do I get my 3D plots look as given in textbooks, ie. with the y-
> axis pointing to the right, the z-axis up and x-axis pointing out of
> the paper/screen ( showing the first octant)?  I mean the kind of
> plots one draws on paper when working out surface integrals  in
> Calculus classes.
>
> If this is of any help, I'd like to get the plot of  the paraboloid
>
>  z = 2-(x^2+y^2),  as given in Fig. 10-10  of  Spiegel's Advanc=
ed
> Calculus, Schaum Series.
>
> I tried
>
>         Plot3D[2 - (x^2 + y^2), {x, -a, a}, {y, -a, a}],
>
> with various values of a. Unfortunately, none of them look like the
> traditional cap-shaped paraboloid.
>
> Thanks for any help.
>
> Sid.



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