Subject: How to plot a projective variety in Maxima?
From: Jaime Villate
Date: Fri, 12 Apr 2013 13:21:08 +0100
Or perhaps you might also see it represented in 3D, using plot3d?
(%i8) plot3d (rhs(answ[1][1]), [x,-5,5], [y,-5,5], [z,-10,10]);
Jaime
On 04/12/2013 01:14 PM, Jaime Villate wrote:
> On 04/12/2013 04:07 AM, Jianrong Li wrote:
>>
>> I am trying to plot the projective variety defined by the homogeneous
>> polynomials xz-y^2 = 0, yw-z^2 = 0, xw-yz = 0. I am trying to use
>> implicit_plot function in Maxima. But it is not successful. How could
>> I plot this variety? Thank you very much.
>>
> Perhaps this can be useful?:
>
> (%i1) display2d: false$
> (%i2) eq1: x*z-y^2$
> (%i3) eq2: y*w-z^2$
> (%i4) eq3: x*w-y*z$
> (%i5) system: eliminate([eq1,eq2,eq3],[w]);
>
> (%o5) [z*(x*z-y^2),x*z-y^2]
> (%i6) answ: map(lambda([e],solve(e,z)),%);
>
> (%o6) [[z = y^2/x,z = 0],[z = y^2/x]]
> (%i7) ploteq (rhs(%[1][1]));
>
> An you can then click in a few points and use the "save" icon when you
> are happy with the result.
> In to make ploteq work, you need to have xmaxima installed (see
> http://maxima.sourceforge.net/docs/manual/en/maxima_22.html#SEC111)
> Regards,
> Jaime
>
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