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

[Leo B. <leo...@um...>]

Leo Butler <leo...@um...> writes:

> Try f^(1/3); f vanishes to 4th order at (0,0) so the numerics are going
> to be bad near there.
>
> Leo

draw2d(grid = true,ip_grid=[100,100],ip_grid_in=[10,10],implicit((f)^(1/3),x,-0.1,0.1,y,-0.1,0.1),terminal=dumb);
                                                            
      0.1 +------------------------------------------+      
          |          :          :         :          |      
          |          :          :         :          |      
          |          :          :         :          |      
          |          :          :         :          |      
          |          :          :         :          |      
          |          :          :   ***   :          |      
          |          :          :  ** *   :          |      
          |          :          : **  *   :          |      
          |          :          : *   *   :          |      
          |          :          :**   *   :          |      
     0.05 |-+........:..........:*....*...:..........|      
          |          :          :*   **   :          |      
          |          :          **   *    :          |      
          |          :          *    *    :          |      
          |          :          *   **    :          |      
          |          :          *   *     ******     |      
          |          :          *  **   ***    *     |      
          |          :          *  *  *** :    *     |      
          |          :          * *****   :   **     |      
          |****      :          *****     : ***      |      
          |   *****  :          ***       ***        |      
          |       *******       **    *****          |      
        0 |-+........:..***************...:..........|      
          |          :          *         :          |      
          |          :          *         :          |      
          |          :          *         :          |      
          |          :          *         :          |      
          |          :          *         :          |      
          |          :          *         :          |      
          |          :          *         :          |      
          |          :          *         :          |      
          |          :          *         :          |      
          |          :          *         :          |      
    -0.05 |-+........:..........*.........:..........|      
          |          :          **        :          |      
          |          :          :*        :          |      
          |          :          :*        :          |      
          |          :          :*        :          |      
          |          :          :*        :          |      
          |          :          :*        :          |      
          |          :          :**       :          |      
          |          :          : *       :          |      
          |          :          : *       :          |      
          |          :          : *       :          |      
          |          +          + **      +          |      
     -0.1 +------------------------------------------+      
        -0.1       -0.05        0       0.05        0.1     
                                                            

(%o21) [gr2d(implicit)]
(%i22) f;

(%o22) 2*y^5-x*y^3+2*x^2*y^2-x^3*y+2*x^5
(%i23) 


>
> Michel Talon <ta...@lp...> writes:
>
>> Hello,
>>
>> to do something with the quaratine, i am studying the chapter on
>> resolution of singularities
>>
>> of algebraic curves in the book by Walker.  So i compute the various
>> Puiseux series of the curve
>>
>> 2*x^5-x^3*y+2*x^2*y^2-x*y^3+2*y^5=0 and at the end i had the idea to
>> plot this curve around (0,0)
>>
>> in order to see how the branches come together with
>> draw2d(implicit(...)). To my surprise the drawing is completely
>>
>> wrong and does not even come close to (0,0) which is an obvious
>> root. I cannot be more precise
>>
>> except joining the computation (with the plots in wxmaxima format)
>>
>> which can even be of help for people interested in the subject, but i
>> would be happy if someone had an
>>
>> idea about this misbehaviour.
>
>
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