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## Re: Folium of Descartes

 From: Muthiah Annamalai Subject: Re: Folium of Descartes Date: Fri, 16 Nov 2007 18:25:31 -0600

```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.
>
> E.g., in Matlab I get:
>
> f = sym('x^3-x^2+y^2');
> ezplot(f)
>
>  \    |
>   \   |
>    \  |  __
>     \ | /  \
> _____\|/____\______
>      /|\    /
>     / | \__/
>    /  |
>   /   |
>  /    |
>
> Which is the correct folium.
>
> In Octave:
>
> f = inline(vectorize(x^3-x^2+y^2);
> x = linspace(-2*pi, +2*pi, 100);
> y = x;
> plot(f(x,y))
>
>           |          /
>           |        _/
>           |       /
>           |     _/
>           |    /
> ______ ___|___/ _________
>      _/   |
>     /     |
>   _/      |
>  /        |
> /         |
>
> Okay, the ASCII-drawings are not so beautiful but I hope they'll render
> the idea :)
>
>
> G.L.
> --
> web: http://heruan.my.aldu.net
>

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.

-Muthu

```