Hi François, 

My aim is to find a way to plot any and all implicit functions, not to plot 
only the lemniscate. But, that is a very interesting Wikipedia entry. Sorry I 
wasn’t clear!

Thanks,

Roger

> On Jan 22, 2022, at 4:37 PM, francois.chaplais via use-livecode 
> <use-livecode@lists.runrev.com> wrote:
> 
> In
> https://en.wikipedia.org/wiki/Lemniscate_of_Bernoulli 
> <https://en.wikipedia.org/wiki/Lemniscate_of_Bernoulli>
> use the formulation in polar coordinates.
> You sample theta, compute the corresponding radius r, convert the polar 
> coordinates to usual cartesian coordinates, and draw a line between each 
> point for successive angles theta.
> 
> This is an explicit formulation (up to the sign or r, but the figure is 
> obviously symmetric with respect to the origin).
> 
> HTH
> François
> 
>> Le 22 janv. 2022 à 21:04, Roger Guay via use-livecode 
>> <use-livecode@lists.runrev.com> a écrit :
>> 
>> Thanks, Thomas. I’ve done some of that but you suggest some better keywords 
>> to search with. I will give it another go.
>> 
>> Roger
>> 
>>> On Jan 22, 2022, at 12:34 PM, Thomas von Fintel via use-livecode 
>>> <use-livecode@lists.runrev.com> wrote:
>>> 
>>> I am not a mathematician, but this kind of equation is called implicit 
>>> function, implicit equation or implicit curve. If you search for that 
>>> combined with draw or plot, you might find explanations. But it seems to be 
>>> complicated.
>>> 
>>> Hope this helps.
>>> Thomas
>>> 
>>> 
>>> 
>>>> Am 22.01.2022 um 17:56 schrieb Roger Guay via use-livecode 
>>>> <use-livecode@lists.runrev.com>:
>>>> 
>>>> This equation for the lemniscate, (x^2+y^2)^2 = 100*(x^2-y^2) is an 
>>>> example of a 2 variable function f(x,y). I am trying to figure how to plot 
>>>> such functions in LC. I can do simple functions like y = f(x) and x = 
>>>> f(t), y = f(t). Calculators such Good Grapher on the Mac do these f(x,y) 
>>>> functions with apparent ease. How? 
>>>> 
>>>> The only thing I’ve come up with so far is to imbed a y-repeat loop within 
>>>> an x-repeat loop where for each value of x (within a certain range), every 
>>>> value of y (within a certain range) is tested for the equation being true. 
>>>> If true, a point is generated in a point list of a polygon. I think, in 
>>>> principle, this should work and with persistence, I might be able make it 
>>>> work, but so far, no cigar. 
>>>> 
>>>> Is there a better way?
>>>> 
>>>> 
>>>> Thanks,
>>>> 
>>>> Roger
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