Re: [Maxima-discuss] Problem with draw2d(implicit(...))

[Gunter K. <gu...@pe...>]

On 20.03.20 23:38, Thomas D. Dean wrote:
> On 2020-03-20 15:34, Robert Dodier wrote:
>> On Fri, Mar 20, 2020 at 3:10 PM Michel Talon <ta...@lp...>
>> wrote:
>>
>>> You are right, this is closer to what the plot should look like.  I
>>> have also tried with maple
>>> as said by Thomas, it gives a very poor plot which looks quite the
>>> same as your own.
>>> Apparently this is a very difficult problem for those plotters since
>>> the "rabbit ears" should
>>> extend to (0,0) as shown by the plot of the Puiseux series. Now i
>>> understand how the Puiseux
>>> developments are to be connected, precisely by these rabbit ears.
>>> You can see that on some range of
>>> x there are 5 solutions to f(x,y)=0  and less in other ranges
>>> because some solutions become imaginary.
>>
>> I don't understand why some methods for plotting this function work
>> better than others. In addition to the ones already mentioned, there
>> is also implicit_plot which yields yet another picture. Can someone
>> explain why different methods give different results here?
>>
> I think the number of points in the plot makes a difference.  Varying
> the number pf plots in Maple, I can make the plot not show the rabbit
> ears or to through 0,0.
>
> In gnuplot, I believe bins=xxx controls the number of points used in
> the plot.  How can this be passed through from Maxima?
>
draw3d(
    xu_grid=500,
    yv_grid=500,
    contour='map,
    contour_levels=10,key="test",
    explicit(
        2*x^5-x^3*y+2*x^2*y^2-x*y^3+2*y^5,
        x,-.2,.2,
        y,-.2,.2
    ),
    grid=true
)$