Yes, and I should have thought of that!
Fernando
On 3/5/2020 12:13 PM, Dima Pasechnik wrote:
In fact, substituting x and y directly into the equation of the curve
to plot, and clearing denominators,
produces something pretty good,IMHO:
implicit_plot(v^2*3*sqrt(1-u^2-v^2)-u^3*9+u*(1-u^2-v^2),(u
More conceptually, one can use, with care, Sage's substitution facilities:
sage: var('u v x y t');
sage: f=y^2-x^3+x
sage: fs=(f.subs(x=u*3*t^(-1/2),y=v*3*t^(-1/2))*t^(3/2)).expand() #
only works with extra variable t
sage: implicit_plot(fs.subs(t=1-u^2-v^2),(u,-1,1),(v,-1,1))
On Thu, Mar 5, 2020
In fact, substituting x and y directly into the equation of the curve
to plot, and clearing denominators,
produces something pretty good,IMHO:
implicit_plot(v^2*3*sqrt(1-u^2-v^2)-u^3*9+u*(1-u^2-v^2),(u,-1,1),(v,-1,1))
On Thu, Mar 5, 2020 at 4:51 PM Dima Pasechnik wrote:
>
> On Thu, Mar 5, 2020
On Thu, Mar 5, 2020 at 2:32 PM Fernando Gouvea wrote:
>
> This works, in the sense that there's no error. One does get a bunch of
> extraneous points near the boundary of the disk. It's as if plot_points were
> trying to connect the point at (0,1) and the point at (0,-1) along the
> circle, eve
This works, in the sense that there's no error. One does get a bunch of
extraneous points near the boundary of the disk. It's as if plot_points
were trying to connect the point at (0,1) and the point at (0,-1) along
the circle, even though f_uv is 1 on the circle.
Strangely, they occur only on
The easiest way is to use Python functions rather than symbolic ones;
define a function that is 1 outside the unit disk, and implicitly plot it.
sage: def f_uv(u,v):
: if u^2+v^2>=1:
: return 1
: else:
: x=u*sqrt(9/(1-u^2-v^2))
: y=v*sqrt(9/(1-u^
Here are the currently recommended lists of system packages to be installed with
apt-get, as of https://trac.sagemath.org/ticket/29273
$ sudo apt-get install bc binutils bzip2 ca-certificates cliquer
curl g++ g++ gcc gcc gfan gfortran git glpk-utils gmp-ecm lcalc
libboost-dev libbz2-dev libcli
