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## Re: Folium of Descartes

 From: Giovanni Lovato Subject: Re: Folium of Descartes Date: Mon, 19 Nov 2007 19:28:50 +0100 User-agent: Thunderbird 2.0.0.6 (X11/20071022)

```Muthiah Annamalai wrote:
> On Nov 16, 2007 1:45 PM, Giovanni Lovato <address@hidden> wrote:
>> Muthiah Annamalai wrote:
>>> Giovanni Lovato wrote:
>>>> How can I draw the Folium of Descartes in Octave?
>>>> In Matlab I did:
>>>>
>>>>
>>>>>> f = sym('x^3-x^2+y^2');
>>>>>> ezplot(f)
>>>>>>
>>>> Various Octave tutorials explain how to draw simple functions in one
>>>> variable, but I can't find a way to draw functions in two (or more)
>>>> variables.
>>>>  I'm a very newbie of Octave (and Matlab too), maybe it's silly
>>>> questions - in this case, sorry :)
>>>>
>>>> G.L.
>>>>
>>> Apparently the right (I dont have Matlab, so I assume here) way, to do
>>> this is
>>>
>>> func = inline ( vectorize ( 'x^3-x^2+y^2' ) );
>>> y = linspace(-2*pi, + 2*pi, 100);
>>> x = y;
>>>
>>> z = func(x,y);
>>> plot3 (x,y,z)
>> Thank you for the interest!
>> BTW the plot won't display a folium-like curve, but a totally different
>> (I think!) curve.
[CUT]
>>
>
> Im sorry for flooding the list. I am using a new mail client, but
> thats no excuse.
> I think you want to plot the 'implicit' functions here in the ezlpot().
> I think I missed that point earlier.

Yes sorry, I didn't explain well (and I'm not so cute in speaking English)!
I would be able to draw the implicit function F[X,Y] : X^3-X^2+Y^2 = 0
like ezplot() in Matlab does. I thought there was a simple and common
solution on doing it, but if this is a weird request I'll try to draw it
manually with a vector-graphics tool.
Meanwhile I'll remain tuned on this list to catch any other hint :)

Thank you!
G.L.
--