Is there a way to plot a function of (x,y) like ezplot in Matlab?

[sfan]

Hi, guys

I want to plot the function:

f(x,y) = x^2 + y^2 +x*y - 3600, bounded with f(x,y) <=0;

Just like the graph shown below:

The figure is plotted with ezplot in Matlab.

function a=elp1(x,y)

     a=x.^2+y.^2-60^2-x.*y;

end

figure(1)

h1=ezplot('elp1',[-90,90,-90,90]);

So far I haven't figured out an alternative in Mathcad that can do this.

Could you help me with some ideas?

Thank you very much!

Best

Shawn

[-MFra-]

Hi Shawn Fan,

your function is a quadric which can be plotted as follows:

the 2D plot looks like the intersection of the quadric with a plane parallel to the xy plane (z=f(x,y)=a).

For me this is the most simple and basic method ...

Best Regards

FM

[ValeryOchkov · Accepted solution]

One general method for any f(x, y)

[ValeryOchkov]

Lace

[sfan]

Thank you Valery!

This is very helpful!

Could you give me some hint on how you apply the approximate equal?

I use a Greek beta letter to substitute your approximate equal sign since I don't know how to input it in Prime.

When I type f(x,y) and the beta sign, Mathcad will always place a "." in between the two terms, making that beta a variable rather than an operator.

Best

Shawn

[ValeryOchkov]

More correct the approximate equal:

[sfan]

Like this, there is a "." sign automatically inserted when I type Beta

[ValeryOchkov]

And than use infix operator!

[sfan]

Thank you!

Unfortunately I am using Mathcad Prime now and it appears that Prime cancels the infix operator (so sad)

I would use the convergence of say f(x,y) <= 0 to generate a solid(with many points) circle then.

So sad Prime cancels this useful function that looks like a devolve.

Considering Matlab recommends fplot over the old ezplot, while fplot does not come with the same function as ezplot, I feel a little bit better, LOL...

Still, thank you Valery, thank you FM!

[ValeryOchkov]

Prime - three plane 2-d degree curves

[Werner_E]

An ingenious method implemented by Viacheslav  N. Mezentsev to do implicit 2D and 3D plots (even for Prime) can be found here:

Re: implicitplot2d()

[sfan]

Thank you so much Werner!

This function is very quick!

I will refer to Mezentsev in my homework.

Thank you!

[ViktorKorobov]

Another method from Viacheslav A.Tarasov. It works in MC 15 but does not work in the Prime (why?).

Viktor

[Werner_E]

Here is a way to simulate it in Prime

Its a pity its not possible to do it the way it works in real Mathcad

Alas - its Prime - what did we expect?