Re: Plotting curves defined by implicit functions

[kingcrimson]

> Il giorno 16 set 2019, alle ore 16:55, Brett Green <address@hidden> ha 
> scritto:
> 
> Thank you! I've used contours for this before, and was wondering if there was 
> an alternative method streamlined for level curves, but that's probably just 
> a pipe dream.
> 
> On that subject, though, I have an issue with contour. Either I'm doing 
> something mathematically inane or I'm misunderstanding how to call the 
> function. I rune the code:
> 
> F = @(x,y) x.^2+y.^2-4;
> x=linspace(-5,5,100);
> y=x;
> for k=1:100
> for j=1:100
> Fmat(k,j) = F(x(k),y(j));
> end
> end
> contour(x,y,Fmat,0)
> 
> and get
> 
> warning: division by zero
> warning: called from
>     __contour__ at line 167 column 11
>     contour at line 74 column 18
> 
> I thought I asked for a contour where Fmat=0, which should be a circle of 
> radius 2. What am I missing here?
> 
> - Brett Green



>> F = @(x,y) x.^2+y.^2-4;
>> [x, y] = meshgrid (linspace (-5,5,100));
>> contour (x, y, F(x, y))


have a look at meshgrid in the manual.
c.