Plotting an implicit function?
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I have the following equation:
F(x,y) = sqrt( (x^2 * y)^-0.2))
where x and y are positive.
The general shape should look like this:
and I was wondering how I would go about plotting that in matlab, after my unsuccessful attempts with ezplot.
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Matt J
le 21 Déc 2014
Modifié(e) : Matt J
le 21 Déc 2014
You could use ezplot, e.g.,
>> F=@(x,y) sqrt((x.^2.*y)-0.2)
>> ezplot(F,[0,2]); shg
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John D'Errico
le 21 Déc 2014
Modifié(e) : John D'Errico
le 21 Déc 2014
Therein lies the problem with the internet. Some random person can post a web site that makes any claim they want. You need to think about what you see and decide if it makes sense, or it is simply a pusher of mental pablum. This is true in general, and of course true in mathematics.
An implicit function only makes sense IF there is an equality in there. Otherwise, you have nothing. So what is F(x,y) equal to? Perhaps 1? 0? pi? 17? Ah! Yes it must be 42.
My point is, you will generally see different curves, depending on the value of that unspecified right hand side. Lacking anything else provided by you, MATLAB makes the perfectly reasonable assumption that it must be zero, and that any necessary constant was built into the function F as provided by you. Any other assumption would simply be wrong.
Since you seem confused, I'll offer a web site ( wikipedia ) that explains what is an implicit function. Of course, then you need to read and decide if what you see is true. I might make note of the form it shows, with an equality and a right hand side of zero. I'm not saying that Wikipedia is perfect of course, hey it could be a lie.
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